Minix vs. Unix/Xenix (was Re: dosread.c)
John C. Archambeau
>In article <695.25...@mudos.ann-arbor.mi.us> m...@mudos.ann-arbor.mi.us (Marc Unangst) writes:
>>I'm not Andrew Chan, but I can tell you the things MINIX lacks
>[Summarized]
>
> 1. Large model. A real ugly hack forced by the brain damaged Intel
> architecture. MINIX doesn't inherently have an 64K limit. On the
> Atari you can have programs as large as physical memory. I expect
> the arrival of the 386SX will spell the end of the 8088 and 80286
> within a couple of years. At that point we can adopt a single linear
> 32-bit address space, like MINIX-ST.
The end of the 80x86 (x < 3) will come when Micro$oft quits supporting MS-DOS.
Read the Byte article (April '89, I believe) on the 286 vs. 386SX. The
286 has at least a 10 year lifespan according to AMD and Harris which make the
high speed 286's (16 to 25 MHz, with Harris making the only CMOS 286's). A
286 box makes a decent file server.
> 2. Virtual memory. I tend to regard this as obsolete. With Bruce Evans'
> protected mode kernel and a 2M 386 you can have up to 2M of programs
> running at once. That has to be enough for a personal computer.
> Thus I see virtual memory as something with a lifespan limited to
> the older machines, which will probably be gone in a couple of years.
The closer Minix comes to real Unix or even Xenix, the more demand for virtual
memory. GNU C easily gulps 1 Mb of RAM on the Atari ST whether it's running
from Minix or TOS. If you are editing a large file in vi, you're going to
need virtual memory. The more real applications that are ported to Minix, the
more the need for virtual memory because of the simple fact that computers
have a finite amount of memory. When SCO and Sun MicroSystems take virtual
memory out of their OS'es, then will believe it's obsolete. For the original
goal of Minix, yes, VM is obsolete, but what about down the line a couple of
years when you get to the 486 or 586? Also, there's the argument for faster
hard drive. If somebody is running a 19ms hard drive on a 386 with 4 Mb of
RAM, I can easily see the need for VM if the OS is being used for real
applications.
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Tom Frauenhofer
>a...@cs.vu.nl (Andy Tanenbaum) writes:
>>In article <695.25...@mudos.ann-arbor.mi.us> m...@mudos.ann-arbor.mi.us (Marc Unangst) writes:
>> 2. Virtual memory. I tend to regard this as obsolete. With Bruce Evans'
>> protected mode kernel and a 2M 386 you can have up to 2M of programs
>> running at once. That has to be enough for a personal computer.
>> Thus I see virtual memory as something with a lifespan limited to
>> the older machines, which will probably be gone in a couple of years.
>The closer Minix comes to real Unix or even Xenix, the more demand for virtual
>memory.
While this may not be pertinent to minix, but on some machines researchers
are using virtual memory techniques where they have access to more physical
memory than their processor can legally address (the BBN Butterfly, for
example). Will virtual memory be gone in a couple of years? No. Maybe
when processors handle larger word sizes, but that's still a few years off.
Thomas V. Frauenhofer ...!rutgers!rochester!cci632!ccird7!tvf
*or* ...!rochester!kodak!swamps!frau!tvf *or* ...!attctc!swamps!frau!tvf
"The Earth? I'm going to blow it up. It obstructs my view of Venus" - Martin