1024 Cyls or Mb's?
Steve Morris
Can anyone answer this for me.
There is a SCSI BIOS limit of 1024 cyls for installing a SCO bootable
partition within. But is it a case of 10024 cyls or 1 Gb - whichever comes
first? I seem to remember something in one of the older SCO manulas I had
that mentioned installing SCO on disks larger than 1Gb.
--
Regards
Steve
Jim
disk.
"Steve Morris" <Stephen...@btinternet.com> wrote in message
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Jeff Liebermann
<Stephen...@btinternet.com> wrote:
>There is a SCSI BIOS limit of 1024 cyls for installing a SCO bootable
>partition within. But is it a case of 10024 cyls or 1 Gb - whichever comes
>first? I seem to remember something in one of the older SCO manulas I had
>that mentioned installing SCO on disks larger than 1Gb.
Open server uses a seperate 15MB EAFS filesystem for booting called
/stand. All the parts and pieces that need to be installed below
cylinder 1024 are in /stand. Only /stand needs to reside in the first
1024 cylinders.
The 1GB limit came from Xenix IDE. I forgot the details.
The 2GB limit is for OpenServer EAFS filesystems.
The 1024 cyl for bootable paritions is from BIOS compatibility issues.
See:
What are the filesystem types that can be used in SCO
OpenServer 5?
http://www.sco.com/cgi-bin/ssl_reference?105852
SCO Filesystems Overview
http://www.sco.com/products/Whitepapers/family/filesy4.htm
--
Jeff Liebermann je...@comix.santa-cruz.ca.us
150 Felker St #D Santa Cruz CA 95060
831-421-6491 pager 831-429-1240 fax
http://www.cruzio.com/~jeffl/sco/ SCO stuff
Steve Morris
1024th cyc lies? (i.e what Mb on the disk).
--
Regards
Steve
"Jeff Liebermann" <je...@comix.santa-cruz.ca.us> wrote in message
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Stephen M. Dunn
$Thanks for the info, but how exactly do I determine where on my disk the
$1024th cyc lies? (i.e what Mb on the disk).
First, some background so that you understand the answer I'm
giving - it's usually easier to remember stuff if you can understand
it.
In the Good Old Days, when the numbers of heads, cylinders, and
sectors per track printed on the hard drive and/or its manual were
what the software used, this was straightforward.
With SCSI, though, the geometry the OS sees is entirely unrelated
to the actual geometry of the hard drive. From a SCSI perspective,
the hard drive is a one-dimensional stream of blocks numbered from
0 through whatever, rather than a three-dimensional array of
blocks numbered from (0,0,0) through whatever. This actually makes
more sense; it permits zone-bit recording (where outer tracks have
more sectors to make better use of the physical size of the tracks)
and automatic substitution of bad tracks (no more bad track lists
to handle). It could also enable me to devise a storage medium
that acts like a hard drive but is fundamentally different;
as long as I can represent it as a collection of blocks, any
SCSI host adapter can use it as if it were a hard drive.
The cylinders, heads, and sectors the OS sees are whatever the
host adapter presents. In the old days, most host adapters
mapped things so that each cylinder was a megabyte, so the
first 1024 cylinders were the first gigabyte.
As hard drives got larger, and it became more common for
people to use hard drives that were over 1024 logical cylinders
with this mapping, host adapter manufacturers started playing
around with larger logical cylinders. If your host adapter's
BIOS or setup utility gives you the option of DOS vs. extended
mappings, that's why - the DOS mapping gives you the traditional
1 MB cylinders (so that DOS is happy) and the extended mapping
gives you larger cylinders (to make more advanced OSes happy). The
manual probably won't tell you exactly what the mapping is.
ATA drives in LBA mode work much like SCSI drives, but at
least you usually get to set and/or examine their mappings
in your machine's BIOS.
If you've already got Unix installed, or if you can wait
until you start the installation, Unix will tell you what the
logical layout of your hard drive is. The following lines are
from ATA drives but you'll see something similar for SCSI:
%disk 0x01F0-0x01F7 14 - type=W0 unit=0 cyls=1025 hds=255 secs=63
%disk 0x0170-0x0177 15 - type=W1 unit=1 cyls=944 hds=14 secs=40
The first drive is an 8 GB (approx.) ATA drive in LBA mode.
The PC reports it as 1025 cylinders x 255 heads x 63 sectors.
So on this drive, I'm free to put the boot filesystem anywhere
except the very end.
The second drive is a 270 MB (approx.) ATA drive in traditional
CHS mode. The PC reports it as 944 cylinders x 14 heads x 40
sectors. Back when this was my boot drive, I was free to put the
boot filesystem anywhere I wanted on it.
If you were to see a line like this:
%disk 0x01F0-0x01F7 14 - type=W0 unit=0 cyls=2200 hds=255 secs=63
that would be an 18 GB (approx.) drive, and you could put the boot
filesystem anywhere in the first 8 GB of it.
--
Stephen M. Dunn <ste...@bokonon.ussinc.com>
>>>------------> http://staff.ussinc.com/~steved/ <------------<<<
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Steve Morris
why in Norton Utilities the number of cylinder reported is over 6800 and
somewhere else I've seen it reported as 1115.
I will check out what SCO tells me when I begin installation.
Thanks again.
--
Regards
Steve
"Stephen M. Dunn" <ste...@bokonon.ussinc.com> wrote in message
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