NeXT FACTS

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Kenton Arthur Radek

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Oct 18, 1988, 1:45:00 PM10/18/88
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FIRST IMPRESSIONS -- The NeXT Computer

by Tom Thompson and Nick Baran

The NeXT Computer
With an optical drive,
a 25-MHz 68030,
built-in floating-point,
digital signal processing,
8 megabytes of RAM,
Unix, and more,
this is a power user's
dream machine-but will you be able
to buy one?


Editor's note: In August, Nick Baran, Tom Thompson, and I at-
tended a marathon, all-day briefing at NeXT's headquarters in
Palo Alto. It was the first time a publication was given an in-
depth look at what surely is one of the most eagerly
anticipated machines in recent memory: the NeXT Computer.
On this and several follow-up visits we saw beta versions of
the hardware, system software, and some early applications. We
met with many of the engineers and programmers who developed
the machine's hardware and software, and we spoke with the man-
agers who are determining where NeXT is going and what role it
will play in the microcomputing community.
We weren't disappointed. This is a milestone machine--one
that in all likelihood will cop machine-of-the-year honors all
around.
BYTE will have ongoing coverage of the NeXT Computer in up-
coming issues. We'll report definitive performance figures, for
example, after we receive and test a production unit. Here are
our first impressions of the beta hardware and software.--FSL

The NeXT Computer
It's been a long wait, but it has finally arrived. In early Oc-
tober, Steve Jobs's NeXT, Inc. unveiled the fruit of its crea-
tive efforts: a workstation referred to as "the cube."
NeXT asserts that the cube, having been designed to meet the
computing needs of the next decade, is "the machine for the
nineties." A bold statement, to be sure, but the cube goes a
long way to bolster that claim: It sports the first commercial-
ly available erasable optical drive and advanced VLSI
(very large-scale integration) technology, and it comes with a
built-in digital signal processor. On the software side, the
Unix-based cube features an object-oriented version of C as its
standard programming environment. It uses Display PostScript to
present a graphical user interface that shields users from the
traditionally user-hostile Unix command syntax, and it offers
easy access to the cube's considerable power.
Targeted initially for the higher-education market, NeXT
built the cube with the feedback of an academic advisory coun-
cil that consisted of researchers and professors from schools
such as Carnegie-Mellon, Stanford, and the University of
Michigan.
The academic bent shows throughout. For example, the digital
signal processor can be programmed for real-time laboratory
work and demonstrations. The cube's large mass storage and
memory capacity make it ideal for accessing substantial librar-
ies of information. And Unix is the multitasking operating sys-
tem of choice in academia.
Although the cube delivers a lot of bang for the buck, it's
priced in the neighborhood of $6500 (all prices quoted are
aimed at the higher-education market), which may, at least ini-
tially, limit its availability to its intended user base: stu-
dents. The cube's rich features list would surely be appealing
to those in nonacademic settings (engineering and science ap-
plications come to mind), but we were surprised to learn that
for now, NeXT has no firm plans to pursue these markets.

Outward Appearances
The cube is starkly simple in appearance and physical layout.
The main computer unit is a matte-black cube measuring 1 foot
to a side. There are no switches, and no indicator lights.
There are two panels covering bays that can hold two 5.25-inch
full-height devices. One bay is occupied by a full-height drive
with a wide slot: a magneto-optical drive. The main system unit
is a power user's dream: the latest generation Motorola 68030
processor and 68882 math coprocessor, plus 8 megabytes of RAM
as standard hardware (a 4-megabyte version of the system is
available). An army of connectors (such as a SCSI [small com-
puter system interface] connector and "thin" Ethernet con-
nector) located along the rear of the computer can hook the
cube to nearly any peripheral device.
The system is designed to avoid the rat's nest of wiring all
too common with complex systems. The entire cube system re-
quires just one power cable, which connects the main unit to a
wall socket. A single 10-foot-long shielded umbilical con-
nects the black 17-inch monochrome monitor to the main unit.
This cable carries power for the monitor, video, keyboard,
mouse, sound I/O, and auxiliary input signals in a complex
shielded array. The black keyboard attaches via a connector to
the base of the monitor, whose housing also contains a small
speaker, stereo earphone jack, two stereo channel jacks, and a
micro-phone jack. A two-button mouse (also black) connects to
the keyboard. The beta cubes we looked at were FCC Class A
certified.
This arrangement is very convenient: Your desk need only ac-
commodate the monitor, keyboard, and mouse, and the ample
length of the umbilical gives you the freedom to place the main
unit well away--say, on a shelf. A key on the keyboard switches
the system's power on or off so you don't have to touch the
main unit at all.

Fine-Tuned for High Throughput
The cube's internal construction mirrors the simplicity of its
exterior. The main unit's cubic housing is made of lightweight
magnesium. Inside are four 32-bit NuBus slots, one of which
holds the system's main CPU board. All the cube's system elec-
tronics reside on this densely packed CPU board, which makes
heavy use of surface-mount devices; the cube is essentially a
single-board computer. With the exception of a bipolar array
used to manage the video display and perform Manchester encod-
ing/decoding for Ethernet communications, all the CPU board's
parts use low-power CMOS components. A power supply mounts in-
side the housing on two screws; the entire box is cooled by a
large, quiet, low-speed fan. The nonswitching power supply can
handle voltages ranging anywhere from 90 volts to 260 V, and
frequencies from 50 Hz to 60 Hz. This means that you can plug
in the same hardware almost anywhere in the world without hav-
ing to set switches. The cube should also prove resistant to
the vagaries of commercial electrical power. Its power supply
generates 200 watts, of which the monitor uses 50 W, and 25 W
is allocated for each slot.
NeXT's design for a workstation for the nineties used four
important strategies. First, when possible, high-performance
components were used. The CPU board is built around the 68030
processor and 68882 floating-point unit, both running at 25
MHz. For SCSI peripherals, the NCR 53C90 SCSI interface chip
provides a maximum 4-megabyte-per-second transfer rate. That's
considerably faster than the 1.5-megabyte-per-second rate of
the older NCR 5380 chip. For mass storage, an optional high-
speed hard disk drive using the SCSI bus is available. This
hard disk holds 670 megabytes of formatted data and has an
average seek time of 18 milliseconds.
However, even a high-performance processor can be slowed to a
crawl if it must service every I/O call, or wait on slow
peripherals. (Steve Jobs put it this way: "MIPS is only one-
third of the equation; sustained system throughput is the
key.") So, the second part of NeXT's design strategy was to
minimize the overhead of communicating to the outside world by
offloading as much I/O from the CPU as possible onto smart I/O
processors managing each peripheral. This happens to be a mat-
ter of necessity given the amount of I/O the cube is doing.
Consider that the cube's synthesized digital sound is handled
by a Motorola DSP56001, a 20-MHz digital signal processing (DSP)
chip. The DSP56001 provides the cube with its ability to
synthesize compact disk-quality stereo sound--no mean feat when
you consider it must handle two channels of 16-bit data sampled
at 44.1 kHz. Although the primary function of the DSP is to
minimize system overhead while processing high-quality sound,
you can program the DSP56001 to manipulate any sort of digital
data, say, signal filtering or image processing (see "The
Cube's Digital Signal Processor" below). The DSP makes the cube
an excellent machine for laboratory and experimental work.
That's only part of the I/O traffic. Looking at the back of
the cube, we counted no less than seven I/O ports. These in-
clude the following:

* A DB-19 monitor port carries all video signals, video data,
control signals, mouse movement, stereo sound, and 12V DC power
to the NeXT monitor. Both the sound I/O data and video data (1
pixel every 10 microseconds) are managed by dedicated DMA
(direct memory access) channels.
* A "thin" coaxial Ethernet port operates at 10 megabits per
second and is driven by an AM7996 Ethernet transceiver chip.
* A DB-9 serial printer port drives the NeXT laser printer (see
"The NeXT Laser Printer" below). This port transfers data at
1.8 mbps when printing at 300 dots per inch, and 3.2 mbps when
printing at 400 dpi.
* A DB-25 SCSI port. Its signals are identical to those of the
Apple Macintosh SCSI port. As mentioned earlier, the SCSI bus
can transfer data to a peripheral at up to 4 megabytes per sec-
ond.
* Two serial ports that use the Macintosh mini DIN-8 serial
connectors and signals. Both serial ports can handle up to
230.4K bits per second synchronously (the same as Apple's
LocalTalk), and 38.4K bps asynchronously.
* A DB-15 DSP port connects to both the asynchronous (SCI) and
synchronous serial (SSI) channels on Port C of the digital sig-
nal processing chip. This port can be used to receive or output
digital data.

Looking inside the case, the main CPU board has two more
ports: a 20-pin connector for the optical disk drive, and a 50-
pin SCSI connector for a hard disk drive. Finally, inside the
cube's housing are four 32-bit NuBus slots. Each slot uses a
Eurocard type C connector. NeXT has implemented a CMOS NuBus
with twice the data rate of the standard NuBus for its back-
plane bus. The CPU board assumes the ID of the slot it oc-
cupies. Although they're not used for outside communications,
each of these devices can make demands on the system.
For digital sound synthesis, there happened to be an off-the-
shelf component--the DSP56001--that could be assigned the job.
Unfortunately, there aren't high-speed processors available that
could deal with the rest of the system's I/O, and certainly
none that could handle the magneto-optical drive. Two custom
VLSI chips were designed to manage the cube's remaining I/O
subsystems. These chips handle the SCSI interface, the magneto-
optical drive (including error-correction logic), the serial
ports, and Ethernet transfers.
Both these chips pack a lot of components: According to NeXT,
each chip contains about 10 times the amount of logic circuitry
used by an entire Mac II.
But there's still a problem lurking here, subtly related to
I/O: how to manage data to and from these I/O processors. If
the CPU must periodically transfer data between memory and the
various I/O processors, the system's performance is still
degraded.
NeXT's third design strategy was to improve data throughput
within the system itself by managing these transfers with
custom DMA hardware. This DMA hardware is implemented in one of
the same VLSI chips that helps manage the system I/O. There are
no less than 12 DMA channels on the main CPU board. They in-
clude the following:

* two Ethernet channels (one for transmitted data, one for
received data),
* one video channel,
* one serial channel (for both serial ports),
* one DSP channel,
* two disk channels (one for the magneto-optical drive, one for
a SCSI hard disk drive),
* one printer channel,
* one memory-to-DMA register channel,
* one DMA register-to-memory channel, and
* two sound channels (one for input, one for output).

For the memory-to-register and register-to-memory DMA chan-
nels, "register" corresponds to a 16-byte register buffer in
the DMA hardware. The contents of these registers can be copied
repeatedly under DMA control to memory. An example of this
would be to copy a background pattern for the video display
into the DMA registers, and then use the register-to-memory DMA
channel to copy the pattern into all of the video memory.
The final aspect of NeXT's overall design strategy to improve
throughput is that when the 68030 processor must access memory,
it attempts to do it efficiently. The 68030's burst read cycle
is used where possible, since this mode allows four long words
(128 bits) to be transferred in 9 clock cycles, instead of 16
clock cycles--roughly twice as fast.

Memory and Mass Storage
One way to improve system performance is to keep as much of the
executable code in memory as possible, particularly where mul-
titasking is concerned. The cube has no problem in this area:
It comes equipped with 8 megabytes of 100-nanosecond SIMM-
mounted RAM. The main CPU board has 16 SIMM (single in-line
memory module) sockets, and 8 of these are populated with the
standard RAM. You can add additional 1-megabit-density SIMMs
in 4-megabyte increments to expand system RAM to either 12
megabytes or the maximum of 16 megabytes.
Also located on the main CPU board are 32K bytes of 45-ns
static RAM. 8K bytes of this SRAM are used for the magneto-
optical disk buffers, and 24K bytes are allocated for the
DSP56001. There are also 256K bytes of dual-ported video RAM
for the video display. A 128K-byte PROM contains the bootstrap
and some diagnostic code for the cube. This bootstrap code
simply loads the Unix kernel and starts it. There are no spe-
cial graphic or system functions similar to the Macintosh Tool-
box embedded in this ROM. The operating system, drivers, and
custom display software reside on the boot drive.
The most interesting peripheral on the cube is its read/write
magneto-optical drive. The optical drive fits into a 5.25-inch
full-height bay on the cube and has a slot to accept an optical
cartridge. The cartridge is removable through a software-
actuated eject mechanism using an internal motor.
The optical cartridges themselves resemble overgrown 3.5-inch
floppy disks, complete with a rigid shell and shutter door, but
the resemblance ends there; each optical cartridge holds a
whopping 256 megabytes of user data. This allows you "to take
your entire world with you" since the Unix kernel, the bundled
applications software, and lots of user data will fit on a
single cartridge.
The optical platter is composed of the same clear rigid
polycarbonate material that's used in CD-ROMs. Embedded within
the platter is a layer of reflective aluminum backing that's
overlaid with a magneto-optical substrate. The platter rotates
inside the cartridge at 3000 revolutions per minute, 10 times
the rotation speed of a CD-ROM, and almost as fast as a hard
disk drive.
How does the magneto-optical drive work? A single laser per-
forms both read and write operations. To write data to the
disk, the drive first applies a magnetic field to the platter.
The orientation of the magnetic field determines the data to be
written to the platter--either a 0 or a 1. The magnetic field
is first oriented to write 0s at the start of what's called the
erase pass.
The laser uses a high-power beam to heat a sector on the
platter's substrate to its Curie point--the temperature at
which the crystals in the substrate "forget" their previous
orientation and reorient themselves to the surrounding magnetic
field. All the data in the target sector is thus erased to 0s.
Next, the magnetic field is oriented to write 1s in the write
pass, and at every spot in the sector where a bit must be set
to a 1, the laser again heats the substrate to the Curie point.
Finally, the sector is read in a verify pass to check the ac-
curacy of the data.
To read data off the platter, the drive removes the magnetic
field, and the laser directs a low-intensity beam at the plat-
ter. The beam travels through the substrate and is reflected
off the aluminum backing. However, in a phenomenon known as the
Kerr effect, the crystal alignment in the magneto-optical sub-
strate alters the polarization of the reflected beam. The
amount of beam polarization determines its intensity as it
passes through a polarizing filter to a photodetector. The beam
intensity indicates whether a 1 or a 0 was read at the spot on
the platter.
The optical drive's I/O processor uses a robust error-
correction coding to protect the integrity of the data read
from the platter. (In addition to the 256 megabytes of user
data, each cartridge carries a 30 percent overhead just for the
error-correction code.) Data and its associated ECC information
is read from the disk and fed into one of two 1296-byte buffers
located in high-speed SRAM. As the data is checked and cor-
rected for errors, it is transferred to the second buffer. It's
the contents of this second buffer that is actually used by the
system.
While the operation of the magneto-optical drive seems simple
in principle, the new technology needed to make this storage
device possible was considerable. NeXT admitted that it had
literally "gambled the company" on this technology becoming
available for use in the cube.
But it did work, and one magneto-optical drive comes standard
on the cube. While the drive is designed to boot and run the
operating system, its 96-ms average seek time may prove a
bottleneck in some applications. For the beta software, if you
were using the magneto-optical drive as the system disk, you
could not remove the cartridge without rebooting the system.
However, NeXT plans to modify the software so you can copy
files to another optical cartridge with a single magneto-
optical drive.
Optical cartridges are expected to cost $50 initially, al-
though the price may fall as they are produced in volume. Since
the cube has room for an extra 5.25-inch full-height device, you
can purchase either a second optical drive for $1495, or the
670-megabyte hard disk drive for $3995.

Getting the Picture
As we used the cube, we couldn't help being impressed by the
crisp quality of its display. This is no accident: The 17-inch
NeXT monochrome monitor has an ample 1120- by 832-pixel display
that contains more pixels than most 19-inch monitors (which
usually have 1024 by 768 pixels). The monitor has a 94-dpi
screen, as compared to the Macintosh's 72-dpi screen. However,
this display is only 2 bits (four gray levels) deep. The
graphic interface looks very good and makes effective use
of the four gray levels.
A 17-inch monitor was chosen for the video display as a com-
promise between display size and weight. On the monitor's base
are two small tractor-style wheels that let you move the
monitor easily across a table surface.
The video display has a bandwidth of 100 MHz, with a vertical
refresh rate of 68.3 Hz. The monitor uses the positive and neg-
ative 12 V DC supplied by the cube's monitor port for power.
Inside the monitor's housing are two boards. A step-up trans-
former on the first board generates the high voltages required
to drive the video tube. The second board handles the rest of
the I/O managed by the monitor: keyboard, mouse, and sound.
The 84-key keyboard connects to a port located on the
monitor's base. The keyboard also has cursor keys, a numeric
keypad, a power-on/power-off key, and pairs of keys that con-
trol the volume and screen brightness (pressing one key in-
creases the chosen output; pressing the other decreases it).
There are two Command keys and two Alt keys (located on oppo-
site sides of the keyboard) that are mapped separately. There
are no PC-style function keys. A two-button optomechanical
mouse also connects to a port on the keyboard.
There are also left- and right-channel analog stereo jacks,
and a jack for stereo headphones on the monitor's base. There's
also a jack for a microphone so you can record sounds through
the monitor, say, for voice mail. This port uses a telephone
codec input that's sampled at 8 kHz, and it uses 8-bit Mu-law
scaling for the digitized data. The data is saved within a
Sound object that can be utilized by the NeXT Unix mail facil-
ity or by NeXT applications.

The Software
As much as the NeXT hardware represents an impressive step for-
ward in areas such as digital signal processing, optical disk
storage, and VLSI technology, the NeXT system software is a
step forward for software technology. The system offers an
easy-to-use graphical interface to Unix and an object-oriented
programming environment for programmers and software devel-
opers.
It's an understatement to say that NeXT expects Unix to catch
on. Steve Jobs told us, "I believe this with every bone of my
body: Unix will be the prime operating system of every major
company in the 1990s."
So it's not surprising that the cube is a Unix-based system.
It features a proprietary windowing system that is designed to
shield the Unix command-line interface (CLI) from the user,
substituting simple point-and-click mouse operations to manage
files and execute applications. NeXT also uses Adobe Systems'
PostScript imaging model (often referred to as Display
PostScript) for displaying all text and graphics on the screen.
Display PostScript is an extension of the PostScript page-
description language (see "Display PostScript" below).
The NeXT system software also includes development tools for
building application interfaces and integrating objects into
application programs. These tools are called the Interface
Builder and Application Kit, respectively.

The Operating System
NeXT uses the Mach Unix kernel developed at Carnegie-Mellon
University. The Mach kernel is compatible with BSD (Berkeley
Standard Distribution) Unix version 4.3, but provides major en-
hancements such as shared memory, fast interprocess communica-
tion, and potential multiprocessing support through the use of
threads. Shared memory allows multiple processes to share com-
mon segments of memory. IPC allows processes to communicate
with other processes and to transmit messages and data between
them. Threads are "lightweight processes" that have their own
execution stack, but within the context of a the task that cre-
ated it (i.e., the thread has access to all the resources made
available to the parent task such as memory, and opened files).
Multiprocessing support is possible by assigning threads to
particular processors. However, multiprocessing is not sup-
ported in the initial release of the NeXT operating system.
Since you can add multiple CPU boards to the cube's backplane,
we can expect to see multiprocessing support in later releases
of the operating system.
In NeXT's first release, the operating system consists of a
single kernel with the Mach implementation of IPC, scheduling,
and virtual memory operating as a layer within the BSD Unix
kernel. However, the ultimate goal of the Mach implementation
is to provide a modular architecture for Unix that would allow
for a much smaller kernel with separate processes dedicated to
file handling, networking, and Transmission Control
Protocol/Internet Protocol (TCP/IP).
Like most Unix-based systems, the cube implements virtual
memory using a paged-memory system to allow applications to run
even if their memory requirements exceed the available physical
memory. Idle portions of a running application are "paged"
(i.e., written to disk) in 8K-byte blocks, called pages. How-
ever, as in all virtual-memory systems, it is possible to over-
load the system with too many applications, causing excessive
paging or "thrashing," which can bring the system to a crawl.
While NeXT was not ready to provide numbers for the amount of
memory consumed by the system software, the 8-megabyte base
memory configuration is designed to allow "three or four" ap-
plications to run simultaneously in addition to the system
software.
For networking, NeXT uses TCP/IP and Sun's Network File Sys-
tem, which has become the standard Unix file-sharing system.
Since the cube comes with an Ethernet interface, it is
"network-ready" for TCP/IP-based networks. The thin Ethernet
cabling allows up to 600 feet of cabling and connection of up
to 30 machines without gateways or repeaters. While NFS does
not require one, a dedicated server is preferable in networks
of more than a few machines, due to performance degradation. In
other words, if you're planning to network a bunch of cubes,
you'll need a dedicated NFS server, or a cube to serve that
purpose.

User Interface and Window Server
NeXT provides a graphical windowing interface to Unix that
hides the laborious Unix commands from the user. While veteran
Unix users still have the option of issuing those intuitive
commands (like grep and ls) within a Unix CLI window called the
Console, most cube users should never have to deal with Unix.
The windowing interface, called the Workspace Manager, provides
all the necessary functions for file management, opening and
closing applications, and communicating with other resources on
the system such as peripherals or nodes on the network.
The main interface screen is called the Workspace. Noticeably
absent from the screen is the ever-present menu bar found on
the Macintosh screen, or on a PC running Windows. Unlike the
Macintosh Desktop, menus can be moved anywhere on the Workspace
and float above any open windows.
Menus are hierarchical, and you can split off subhierarchies
from their parent menus. Windows have scroll bars located on
the left and bottom, and there are small boxes on the window
frame for resizing or closing the window. It also has a "mini-
world" function that collapses the window and its menus into an
icon while the process owned by the window continues to run.
Icons become transparent when they overlay other icons, al-
lowing you to always see everything that's currently available
on the Workspace. The icons of frequently used applications can
be "docked" along the right side of the Workspace for easy
recall.
The Workspace is similar to the Desktop metaphor on the
Macintosh, and the Workspace Manager is analogous to the Mac's
Finder. However, no one will accuse NeXT of copying Apple's
look and feel.
File management operations are similar to those used by the
Mac Finder. When you click on a directory in the Workspace, you
can examine the directory in a number of ways. There is a
"browser window," which displays the directory tree in a window
with the directory hierarchy ordered from left to right on the
screen. This browser window normally lets you see three levels
deep, but you can position the point in the hierarchy where you
wish to view files, or resize the window to examine additional
levels. You can also choose to view the directory as icons
with subdirectories represented by folders, or as a conven-
tional text-only Unix directory listing.
The version we saw was definitely beta, so the final word on
the Workspace will have to wait. Nevertheless, it seems very
intuitive and easy to learn. Its performance seems good, and
the display quality is excellent.
Rather than use an existing Unix window server such as X-
Windows, NeXT designed its own proprietary Window Server. The
Window Server manages all interactions between the windows,
keyboard, and mouse for all applications attached to it. The
Window Server obtains events from the operating system and
handles the ones it can (e.g., resizing a window or moving it
to another part of the screen). If it's not an event that it
can service, the Window Server determines which application can
and dispatches it to that application.
Embedded inside the Window Server is the Display PostScript
interpreter, which acts on the PostScript commands passed to
it. This embedded interpreter executes the PostScript commands
it receives and writes the results into the cube's video RAM,
making it appear on the monitor.
The Window Server supports Mach IPC connections as well as
connections through TCP/IP, allowing other cubes on a network
to access another machine's Workspace. The proprietary Window
Server means that existing applications that run on other Unix
windowing systems will have to be modified to run under the
NeXT windowing system. How-ever, a Unix application that uses
conventional console I/O will run inside the Console window
without modification.

The Development Environment
The primary objectives of the NeXT programming environment are
to simplify the development of interactive user interfaces and
to simplify the creation of new applications through the use of
object-oriented programming. Other systems employing graphical
interfaces--like the Macintosh, for example--are great for the
end user but extremely complex for programmers, particularly in
developing a working user interface. To ease the burden of this
task for the developer, the NeXT system includes tools for
building interfaces to the NeXT windowing system, and also
tools for object-oriented programming.
The NeXT system software includes an ANSI C compiler and an
object-oriented preprocessor called Objective-C, developed by
Stepstone Technologies. Objective-C allows you to define ob-
jects as groups of C procedures. NeXT provides several li-
braries of ready-to-use objects, calles kits, for integration
into Objective-C programs. These kits provide a library of
around 34 objects for implementing the core functionality of a
NeXT application, although a programmer would normally use only
a small subset of these objects. This library is known as the
Application Toolkit, and the Objective-C interface can access
it directly.
Object-oriented programming allows a one-to-one cor-
respondence between objects on the screen and objects in your
program. An object consists of data (called instance variables)
and executable code. If the object is to be visible on the
screen (a window, for example), the code also contains an
entity called drawSelf:: that's composed of C code, Objective-C
code, and PostScript code, which is used to describe the ap-
pearance of the object to the Window Server.
Probably the key concept with respect to user interfaces is
that objects can respond directly to messages generated by user
actions. Rather than having to write lines of conditional
statements in C code to respond to user actions, the user ac-
tions are interpreted as messages other objects can understand.
For example, you might have an object in your program called
"Window," which can understand the "Close" message sent by a
user response.
NeXT provides a program called Interface Builder that allows
you to interactively build user interfaces for your programs.
Interface Builder lets you design the layout of a graphical
user interface by selecting buttons, menus, and other objects
from an object library to include in your application.
This function is somewhat similar to ResEdit on the
Macintosh. However, Interface Builder goes further--it allows
you to define connections between objects. That is, Interface
Builder lets you specify actions for the objects to perform in
response to user actions on other objects. For example, you
could build a Beeper button object into your program interface
simply by selecting a prototype button from Interface Builder's
on-screen inventory, moving it to where you want on the screen,
giving it a label, and assigning an action (say, emit a beep)
to be performed when a user clicks on the button.
This is similar to the function of Hyper-Talk in Apple's Hy-
perCard program. The big difference, however, is that Interface
Builder generates the binary description of the object that you
can integrate into programs. You can also create custom ob-
jects by selecting an object that most closely resembles what
you want and customizing its appearance and behavior. NeXT's
goal is to supply enough objects so that a programmer could
select objects and define their connections, making it possible
to built an application from scratch writing little or no code.
In addition to the Application Kit and Interface Builder, the
NeXT system software includes kits for working with music and
sound. The Music and Sound Kits provide objects for integrating
these features into your programs. There is also a number of
library functions (not objects) that allow you to tap into the
processing capabilities of the DSP. These libraries provide
some 50 functions for performing tasks like fast Fourier trans-
forms, and spectral filtering.
NeXT supports the concept of "shared libraries" in its devel-
opment environment. This means that multiple applications and
processes can share a single copy of executable code from the
object library. Although library sharing was not implemented
when we saw the cube, it should improve performance and reduce
the memory and storage requirements of applications.

Applications
NeXT will bundle several applications with the machine. These
include the word processor, WriteNow, that is owned by NeXT and
is currently distributed by T/Maker for the Macintosh. The sys-
tem software also includes the standard Unix Mail program
equipped with a graphical front end that can attach voice mes-
sages to mail files, a file-searching program called Find, C
and ObjectiveC, a symbolic debugger, and on-line documentation.
It also has educational and reference tools such as Webster's
Dictionary, the complete works of Shakespeare, and Mathematica
from Wolfram Research (see "Bundled Software" below). A per-
sonal text database allows you to automatically index all your
word processing and electronic mail communications so you can
recall documents or memos based on keywords instantly.
An important goal of the NeXT software environment is the de-
velopment of "digital libraries." With its erasable 256-
megabyte magneto-optical disk, NeXT hopes to promote the idea
of easily accessible text databases. In the educational market,
these databases will include encyclopedias, dictionaries,
textbooks, and other reference works.
NeXT's first software release lays the groundwork for the
company's plans for the nineties. The DSP and the kits for pro-
gramming it offer exciting possibilities for new real-time ap-
plications. It will be interesting to see how the software will
be used and what new applications will be developed.

One Giant Step Forward?
The cube is an impressive technical achievement. We liked the
carefully thought-out design that didn't just use fast com-
ponents, but covered every aspect of moving information through
the system. The choice of NuBus for the backplane bus is an ex-
cellent one; it goes a long way toward providing the hardware
support for the cube's planned multi-processing capability.
Considering the amount of information that the machine is ex-
pected to use, the high-capacity magneto-optical drive is a
good design choice. The graphical interface uses the well-
documented PostScript imaging language and goes a long way
toward hiding the uglier side of Unix from the user. The facil-
ity with which NeXT's object-oriented programming environment
reduces the work needed to write an event-driven program is
also impressive.
It is indeed a machine for the nineties. It represents a bold
step forward both in hardware and software design and effec-
tively redefines what constitutes "standard equipment."
However, as we go to press, some big questions remain un-
answered. One relates to the performance of the machine. In our
limited time with several beta cubes, it was difficult to judge
the overall performance. Display PostScript operations were
very fast, putting to rest the controversy of Display
PostScript's performance, at least as far as the cube is con-
cerned.
However, disk read/write operations seemed pretty slow--
perhaps because so much beta debugging code was being carried
along as baggage, and because library sharing was not yet im-
plemented. We saw the magneto-optical disk drive in operation,
but it still had some operating bugs, and its 96-ms access time
might be a source of frustration if it's used as the main sys-
tem drive. At this point, we cannot comment on its reliability.
Another question is whether software developers will support
NeXT. The primary obstacle to the acceptance of Unix in the
general marketplace has been the lack of software applications.
Software developers are faced with choosing between Macintosh,
OS/2, DOS, and now a new version of Unix with a proprietary
windowing system. To be successful, NeXT will need substantial
support from software developers; at the time of our visit,
only about 10 developers had signed on, and NeXT would not
release their identities.
The concern about outside development is perhaps tempered by
two facts. First, the object-oriented environment should
simplify moving existing Unix programs to the machine. Second,
each cube is a complete development system, since all the de-
velopment tools--compilers, object libraries, and Interface
Builder, are bundled with the machine.
Then there's the question of NeXT's target market--higher ed-
ucation. While the machine is certainly a perfect fit for the
university community, universities are not known for being big
spenders. Certainly, many students will have a hard time coming
up with $6500 or more for a computer, let alone another $1995
or so for the laser printer, and perhaps $1495 for a second
magneto-optical drive for backups.
Of the cube's design, Jobs told us, "If you want to make a
revolution, you have to raise the lowest common denominator."
That's true, but you also have to get the product into the
hands of enough revolutionaries to make a difference. Yet it's
clear NeXT is thinking small, at least in terms of initial
marketing.
Dan'l Lewin (NeXT's vice president of marketing and sales)
told us, "We built the company not to need huge numbers." And
Jobs said, "We'll focus on other markets in the future, but
we're not going to do it today. There's no reason why we can't
do very well in [the educational] market alone."
Perhaps. But considering the machine's capabilities, we can't
help but wonder if NeXT is being too conservative in its
marketing plans. If so, it seems that NeXT may have to be able
to endure some lean years until the machine catches on in the
early nineties.

The Cube's Digital Signal Processor
The Cube comes equipped with a Motorola DSP56001, an 88-pin
CMOS chip designed for data-intensive real-time signal process-
ing applications. At the core of the chip are three execution
units--data arithmetic logic unit (ALU), address-generation
unit, and program-control unit--that operate in parallel to
provide the necessary throughput.
The DSP works with 24-bit digital data, providing 144
decibels of dynamic range. Two internal 56-bit accumulators
provide 336 dB of dynamic range during arithmetic operations so
the precision of the intermediate results is retained during
data processing.
The DSP56001 is programmable, allowing it to be tailored for
a specific purpose. The 16-bit address-generation unit, com-
bined with hardware select lines for program code or data, can
access three separate 64K words of an external memory space
(192K words total, where a word is 24 bits of data).
The DSP56001 has on-chip program memory composed of 512- by
24-bitwide RAM cells, of which the bottom 64 cells are used for
interrupt vectors. DSP programs can occupy the remaining
memory, or if they're large, they can reside in the external
program space. In the latter case, the on-chip program memory
can serve as a fixed cache. Program instructions are 24 bits
wide, and each bit is significant.
On the cube, the DSP56001 is clocked at 20 MHz, and instruc-
tions exe-cute every two clock cycles to give the chip a 10-
MIPS (millions of instructions per second) rating. The DSP in-
struction set consists of 62 mnemonics that include math, logi-
cal, bit-manipulation, loop, and program-control instructions.
The math instructions encompass such operations as absolute
value, add, subtract, shift left/right, shift left/right and
add (useful for implementing the butterfly computation in
certain fast Fourier transforms), compare, signed multiply,
signed multiply and accumulate, and signed multiply accumulate
and round (MACR).
All these instructions--notably some of the math instructions
just mentioned--are not pipelined and execute in one instruc-
tion cycle (two clock cycles). For example, as the MACR in-
struction executes, an instruction prefetch, 24- by 24-bit mul-
tiply, 56-bit add with convergent rounding, two data moves, and
two pointer updates are performed, and all within one instruc-
tion cycle. Such powerful instructions are possible because of
the parallel operation of the three execution units. These pow-
erful arithmetic instructions, coupled with its high through-
put, allows the DSP56001 to literally process data on the fly.
Inside the DSP56001 are four 24-bit bidirectional data buses:
X, Y, program, and global. Digital data is split into X and Y
components and can be treated as such in two separate 64Kword
external memory spaces. On the cube, 24K bytes of static RAM
provides 8K words of contiguous scalar data, or 4K words of X
and Y data. How this data is ordered in SRAM on the cube is
determined by what range of addresses you write into in the
chip's external memory space.
The two 56-bit accumulators in the data ALU can operate on
the X and Y data sets in parallel. Breaking the data into X and
Y components provides certain advantages. For example, the data
can be treated as X and Y coordinate data for image processing
or graphics, or as real and imaginary components for complex
math, or as coefficients and data for digital filtering. Each X
and Y data bus has an on-chip memory composed of 256- by 24-bit
cells that is used to improve performance. The program bus
prefetches DSP program instructions into the on-chip program
memory. The global bus is used for internal data routing within
the DSP.
The DSP56001 has three I/O ports: A, B, and C. Port A has a
24-bit bidirectional data bus, and the address unit can access
external memory for off-chip program code or data. Various con-
trol lines determine operations such as whether to access pro-
gram or data memory, X and Y data, and if the operation is a
read or a write.
Port B handles 8-bit data to and from a host processor that
could be a CPU, DMA (direct memory access) hardware, or even
another DSP. Control signals for this bus permit interrupt-
driven or DMA transfers of data.
Port C consists of two full-duplex serial ports. The first
port is the serial communication interface (SCI) that provides
standard asynchronous rates up to 312.5K bits per second, and
up to 2.5 megabits per second for synchronous data transmis-
sion. Although these signal timings are RS-232C-compatible, the
voltage levels range from 0 volts to 5 V, so a line driver is
required to produce a true RS-232C signal.
The second port is the synchronous serial interface (SSI) and
is a programmable serial interface. You can set the number of
bits per word, protocol, clock rate, and mode as required to
transfer data at up to 5 megabits per second to and from a va-
riety of peripheral devices.
An example of the DSP56001's processing capability is given
by one of Motorola's application notes, where the chip is used
as a 10-band graphic equalizer for a digital stereo system. In
this document, a compact-disk digital stereo signal (two chan-
nels of 16-bit data sampled at 44.1 kHz or 88,200 16-bit digi-
tal samples a second) goes through the DSP56001's SSI on port
C. Next, realtime digital filtering is performed on 20 bands
(10 bands per channel), and the filtered data returns to the
stereo system, again via the C port's SSI. This admittedly
down-to-earth example shows the processing power that the
DSP56001 can bring to bear on a problem. The sampling rate of
the DSP56001 depends on the amount of data processing going on
at the same time, but it can reach a maximum of 1.66 megawords
per second.
As a computer peripheral, you could use the chip in any num-
ber of applications: speech synthesis, voice recognition, high-
speed modems, image processing, two-dimensional graphics, and
real-time filtering of digital data. Although the signed 24-bit
resolution may seem limiting for some scientific and engineer-
ing applications, you can always use the cube's math coproces-
sor. But for those problems that do fall within this range, the
DSP56001 will be more than adequate.

The NeXT Laser Printer
Let's face it: There are certain situations in your computer
work where you must have printed output. NeXT's answer to this
problem is a low-cost 400-dot-per-inch laser printer. There's
no entry-level dot-matrix printer offered; NeXT is banking on
users preferring laser-printed output. Since the cube handles
screen imaging with Display PostScript, it also makes sense to
take advantage of a high-resolution PostScript-compatible
printer. The printer costs $1995. The NeXT printer is built
around a custom-designed laser engine based on the Canon LBP-SX
laser engine. It can print eight pages per minute and uses the
same toner cartridge as the Apple LaserWriter II printers. A
user-selectable printing mode lets the printer produce pages at
either 300 or 400 dpi. The printer has its own power cord, and
the power supply is set for 110 volts or 220 V levels with a
switch.
The printing process involves imaging the page inside the
cube using Display PostScript, and then bit-blasting it to the
printer. This is similar to the method used by Apple's Laser-
Writer IISC, except that the cube uses Display PostScript, and
the Mac uses QuickDraw. Since massive amounts of data must be
transferred to the printer to produce a page, the printer port
has its own direct-memory-access channel.
One limitation of the printer is that it will only work with
the cube. Also, you cannot network it like PostScript printers
that use Apple's LocalTalk, although you could use a cube with
a NeXT laser printer to act as a print server on a network. The
cube can print to non-NeXT PostScript printers using its serial
ports and Unix printer drivers.

Display PostScript
Display PostScript is an extension of Adobe's PostScript page-
description language (PDL) and is designed as an imaging model
for graphics displays. In theory, software developers could
write the display portions of their applications just once
using Display PostScript: These applications would run without
modification on any computer and operating system that supports
Display PostScript. Another major benefit is that the image on
the screen would reproduce identically on a printer supporting
the PostScript PDL.
Display PostScript is device-independent, an important fea-
ture when you consider that specific dimensional sizing is
display-dependent in most graphics handlers. For example, if
you write a Display PostScript routine to draw a 2inch square
on the screen, the routine will always draw a 2-inch square on
any display supporting Display PostScript, regardless of the
resolution, color capability, or size of the output device. In
other words, Display PostScript permits a "non-unitized" des-
cription of an image until it is interpreted for a particular
display.
This non-unitized approach is in contrast to pixel-based
graphics handlers that can only handle proportional sizing. Of
course, you can also specify proportional sizing in Display
PostScript. Additionally, Display PostScript automatically uses
the maximum color capabilities of the host display, whether it
has just black and white, or 16 million colors. The programmer
does not have to worry about the characteristics of the output
device while writing the application.
The core of Display PostScript is called the DPS Kernel. The
DPS Kernel is an interpreter that translates PostScript
routines into the images on the screen and is designed to be
machine-independent. The DPS Kernel is supplied precompiled in
object format to the OEM.
In addition to the Kernel, Adobe supplies the OEM with
"front- and backend" adapters that consist of source code for
interfacing to the display devices, the operating system, and
the windowing system. The Display PostScript adapters become
part of the host computer manufacturer's system software. Of
course, modifying these adapters for the host computer system
is not a trivial task, and it is usually undertaken by the OEM
as a joint or cooperative effort with Adobe Systems. Again, the
important point here is that the software developer need not
worry about these "adapters."
The main underlying concept of Display PostScript is to iso-
late the display operation from not only the host computer's
operating system but also from its windowing system. The core of
Display PostScript fits inside the Lhost windowing system, which
in this case is the NeXT windowing system, although it could be
anything from Microsoft Windows to X-Windows to QuickDraw.
While the windowing system handles functions such as cut,
paste, and copy, and manages the window boxes on the screen,
Display PostScript handles the actual painting of the window's
contents. Thus, routines for displaying icons, text fonts, and
graphics images have to be written only once using Display
PostScript. However, the software developer still has to write
separate window calls for each windowing system.
Programmers can use the Display PostScript language directly,
or they can use a library of C procedures called PSWrap, which
is recognized and interpreted by the DPS Kernel.
NeXT fully supports the PSWrap library, but has added many of
its own procedures. Some of these are used by the Application
Kit to create and manage windows; other procedures handle
events, mouse, and cursor operations; and still others support
"compositing."
The compositing procedures are multi-bit pixel operators
designed by NeXT's sister company, PIXAR. Each pixel has two
values associated with it: its data value (or color), and its
alpha value (the data's transparency or opacity). On the cube's
2-bit display, compositing makes an icon transparent as it
moves over another object on the screen. These compositing op-
erators are easily extendable and will allow the NeXT software
to migrate to color displays when the time comes.
From brief glimpses of alpha versions of Display PostScript,
several industry observers have concluded that Display
PostScript has serious performance problems--it is too slow.
Adobe Systems vehemently denies this and says critics have
jumped to conclusions based on these preliminary demonstra-
tions. -Adobe says Display PostScript is very fast provided the
code is written properly.
A number of techniques have been developed to improve Display
PostScript's performance, including a binary preprocessor (de-
scribed below), graphic state objects (multiple PostScript
graphic states that can be switched quickly by changing a
pointer), and user paths (an aggregate of PostScript drawing
commands that represent a PostScript path). NeXT uses these
techniques and its own compositing functions to boost the speed
of the display.
As an example of how binary encoding works, say we want to
issue the PostScript operator 72 426 moveto. Normally the DPS
kernel would have to translate the ASCII digits 72 and 426 into
a floating-point format, and the ASCII moveto operator into a
binary code. A lookup table uses this binary code in the DPS
Kernel to steer execution to the routine that implements the
moveto operation. A NeXT application normally calls a PSWrap
function, PSmoveto(fs1>), that passes the IEEE 754 floating-
point values of the numbers to the DPS Kernel, along with the
corresponding binary code for moveto. This effectively
eliminates the overhead of the ASCII translation stage for the
DPS Kernel. The NeXT DPS Kernel can process ASCII PostScript
commands if required.
Display PostScript has one major limitation in that it does
not support three-dimensional imaging. It is therefore not
suitable for CAD software. Adobe admits that Display PostScript
is not intended for high-end mechanical design applications.
(Steve Jobs said that NeXT will support the Renderman Standard,
which he called "the PostScript of three-dimensional
graphics.")
Display PostScript has some very compelling features for
software designers and for end users. It could greatly facili-
tate the porting of software applications across incompatible
hardware systems. But the various competitors for display
standards--such as IBM and Apple--will have to make some com-
promises before Display PostScript can succeed. Until these
compromises are made, both the end user and the software devel-
oper will continue to be plagued by an incompatible world of
competing display standards.

Bundled Software
Here is a list of the software that is scheduled to be bundled
with the NeXT Computer. It includes the Mach operating system
and its development software. Also included are the works of
Shakespeare, a dictionary, and a thesaurus.
You can call up quotations or the dictionary entry for a
specific word at any time by using the cube's Find function.
This capability would be valuable not only to college students
and faculty members, but to anyone who has to write
frequently--whether it's a business proposal or a technical
document.

System software:
Mach operating system
PostScript Window Server and fonts
System administration tools

Development tools:
GNU C compiler
GNU debugger
GNU EMACS
Objective-C 4.0
Berkeley Unix utilities
Terminal emulator
Window-based text editor
Interface Builder

Object-oriented software kits:
Application Kit
Sound Kit
Music Kit
High-speed text-retrieval application (called "Find")

Standard reference works:
Merriam-Webster's Ninth New Collegiate Dictionary
Merriam-Webster's Collegiate Thesaurus
The Oxford Dictionary of Quotations

Documentation for all bundled software:
User's and programmer's manuals

Literature:
Oxford University Press' William Shakespeare: The Complete
Works
User-created text files, such as mail or documents

Applications:
Personal text database
Electronic mail application with graphical interface and
ability to attach voice messages
Word processor
Window-based file manager
Mathematica (Wolfram Research, Inc.)


Kenton Arthur Radek

unread,
Oct 18, 1988, 8:05:35 PM10/18/88
to

Henry Spencer

unread,
Oct 25, 1988, 3:06:55 PM10/25/88
to
In article <23...@sri-unix.SRI.COM> kr...@andrew.cmu.edu (Kenton Arthur Radek) writes:
>... The main unit's cubic housing is made of lightweight magnesium...

That's gonna be fun if you ever have a power-supply fire!
--
The dream *IS* alive... | Henry Spencer at U of Toronto Zoology
but not at NASA. |uunet!attcan!utzoo!henry he...@zoo.toronto.edu

Clayton Cramer

unread,
Oct 27, 1988, 2:20:26 PM10/27/88
to
In article <1988Oct25.1...@utzoo.uucp>, he...@utzoo.uucp (Henry Spencer) writes:
> In article <23...@sri-unix.SRI.COM> kr...@andrew.cmu.edu (Kenton Arthur Radek) writes:
> >... The main unit's cubic housing is made of lightweight magnesium...
>
> That's gonna be fun if you ever have a power-supply fire!
> --
> The dream *IS* alive... | Henry Spencer at U of Toronto Zoology

I don't think that's as much a problem as you think. Back in high
school, some friends of mine and I attached a chunk of magnesium
ribbon to an 8' hydrogen-filled weather balloon (young, foolish, and
lucky to be alive) and attempted to light the ribbon. We made repeated
efforts, and it just would not light with any combination of
firestarting devices we had available. Magnesium powder burns very
nicely (in fact, many powdered metals do well at this), but a solid
mass of magnesium is going to take a lot more flame to ignite than
a power supply. (By the time the case catches fire, I suspect
burning magnesium will be the least of your worries).
--
Clayton E. Cramer
..!ames!pyramid!kontron!optilin!cramer

Jim Mackraz

unread,
Oct 27, 1988, 10:40:29 PM10/27/88
to
In article <6...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
)I don't think that's as much a problem as you think. Back in high
)school, some friends of mine and I attached a chunk of magnesium
)ribbon to an 8' hydrogen-filled weather balloon (young, foolish, and
)lucky to be alive) and attempted to light the ribbon. We made repeated
)efforts, and it just would not light with any combination of
)firestarting devices we had available.

Use a fourth of july "sparkler."

Best if other end of magnesium ribbon is placed in a pile of equal parts powdered
iron oxide and powdered aluminum.

We didn't go aerial in my neighborhood, though. Nice touch. Our thermite
exploits were mostly used to burn holes in a downward direction.

Sorry about further corruption of comp.sys.next bandwidth. I think there
had better be an ID on the optical disks, too.

jimm

--
Jim Mackraz, I and I Computing
amiga!jimm BIX:jmackraz
Opinions are my own. Comments regarding the Amiga operating system, and
all others, are not to be taken as Commodore official policy.

Phil Nelson

unread,
Oct 28, 1988, 1:31:20 AM10/28/88
to
In article <6...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
|In article <1988Oct25.1...@utzoo.uucp>, he...@utzoo.uucp (Henry Spencer) writes:
|> In article <23...@sri-unix.SRI.COM> kr...@andrew.cmu.edu (Kenton Arthur Radek) writes:
|> >... The main unit's cubic housing is made of lightweight magnesium...
|>
|> That's gonna be fun if you ever have a power-supply fire!
|> --
|> The dream *IS* alive... | Henry Spencer at U of Toronto Zoology
|
|I don't think that's as much a problem as you think. Back in high
|school, some friends of mine and I attached a chunk of magnesium
|ribbon to an 8' hydrogen-filled weather balloon (young, foolish, and
|lucky to be alive) and attempted to light the ribbon. We made repeated
|efforts, and it just would not light with any combination of
|firestarting devices we had available. Magnesium powder burns very
^^^^^^^^^^^^^^^^^^^^^

|--
|Clayton E. Cramer
|..!ames!pyramid!kontron!optilin!cramer


The average pocket lighter isn't very hot, really. To get solid Magnesium
going you will need higher temperatures. An electric arc might work.
(Now, where can we find the makings of an electric arc? Power supply?
Yeah, that's the ticket! a power supply! :-) :-)


--
{ames|pyramid}oliveb!tymix!antares!pnelson | Parallel IQ (the IQ of a group)
OnTyme: NSC.P/Nelson POTS: (408)922-7508 | may be easily calculated given
Disclaimer: Not officially representing | the IQ of each member - use the
McDonnell Douglas Corporation policy. | formula for parallel resistance.

William M. Bumgarner

unread,
Oct 28, 1988, 2:08:09 PM10/28/88
to
You had problems lighting the magnesium ribbon... we used to light them
all the time with ordinary lighters... Larger ribbons (thicker) did require
the use of a blow torch.

Considering the heat required to light a ribbon, the next machine will be so
hot that it will burn through a desk, through the floor, and be sittin on the
floor in the basement before the case catches; but to generate that kind of
heat, I would think you would need a nuclear based power supply that suffers
a full meltdown.

We never could find a weather baloon...
b.bum
wb...@andrew.cmu.edu

Another person who is lucky to be alive; but is still young and foolish enough
to blow themselves up and enjoy doing it...

Henry Spencer

unread,
Oct 28, 1988, 4:57:04 PM10/28/88
to
In article <6...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
>> >... The main unit's cubic housing is made of lightweight magnesium...
>> That's gonna be fun if you ever have a power-supply fire!
>... some friends of mine and I attached a chunk of magnesium

>ribbon to an 8' hydrogen-filled weather balloon (young, foolish, and
>lucky to be alive) and attempted to light the ribbon. We made repeated
>efforts, and it just would not light...

Gee, maybe you weren't using the right ignition method. I never had any
trouble! Sure you had magnesium, not something like aluminum?

Moreover, an electrical fire is *hot*. Ever wonder why DEC stopped putting
those cute Plexiglas covers on their power supplies? Plexiglas will burn!


--
The dream *IS* alive... | Henry Spencer at U of Toronto Zoology

Nicholas Spies

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Oct 29, 1988, 1:21:58 AM10/29/88
to
In article <6...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
>...
>mass of magnesium is going to take a lot more flame to ignite than
>a power supply. (By the time the case catches fire, I suspect
>burning magnesium will be the least of your worries).

Mercedes pulled out of auto racing in the 1950's after a magnesium-bodied
car crashed and sent burning debris into the crowd (at Le Mans?). Either
68 or 168 people died (sorry I don't have a reference handy). Definitely more
flame than your average power supply fire would yeild, however...


--
Nicholas Spies n...@cat.cmu.edu.arpa
Center for Design of Educational Computing
Carnegie Mellon University

Tim Maroney

unread,
Oct 29, 1988, 6:32:28 PM10/29/88
to
In article <34...@pt.cs.cmu.edu> n...@cat.cmu.edu (Nicholas Spies) writes:
>Mercedes pulled out of auto racing in the 1950's after a magnesium-bodied
>car crashed and sent burning debris into the crowd (at Le Mans?). Either
>68 or 168 people died (sorry I don't have a reference handy). Definitely more
>flame than your average power supply fire would yeild, however...

The fatality number I recall is in the eighties; horrible accident.
However, please note that a car crash tends to make lots of small metal
fragments, which (in the case of magnesium) would be trivial to light
from a burning gasoline tank, or just from sparks. Now, if the Next
box happens to get involved in an explosion which shatters the case, it
might be worse, but probably not otherwise.
--
Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim
"Mere opinion without supporting argument is no more than the American
Bandstand school of literary evaluation." -- Tom Maddox

Anthony A. Datri

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Oct 30, 1988, 4:46:04 PM10/30/88
to

From my own experiences with Mg ribbon is that the surface tends to oxidize
quickly, and it lights easily with a pocket lighter if you sand it shiny
first.

--
@disclaimer(Any concepts or opinions above are entirely mine, not those of my
employer, my GIGI, or my 11/34)
beak is@>beak is not
Anthony A. Datri @SysAdmin(Stepstone Corporation) stpstn!aad

Anthony A. Datri

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Oct 30, 1988, 4:46:04 PM10/30/88
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