Hard disks with > 1024 Cylindars

[Chip Rosenthal]

In article <1990Aug31.022148.5775 at gpu.utcs.utoronto.ca>
	utgpu!rom!mark, utgpu!rompub writes:
>The disk has 1747 cylindars, 7 head and 54 sectors/track.  [...]  The SCO ODT
>documentation suggests that such a disk is compatible as long as the root
>partition doesn't cross over the 1024 cylindar boundary.

The problem is that the peecee BIOS can't grok more than 1024 cylinders.
Until UNIX is up and flying, you are a slave to the limitations of the
BIOS.  One of the activities during this stage is to load in /boot and
then /unix.  Therefore, they must be accessible by BIOS.  If your root
partition is bigger than 1024 cylinders then /boot or /unix could be
sitting in a region which is inaccessible.  So, limiting /dev/root to
1024 cylinders guarantees they can be loaded.

Some ESDI controllers, such as the WD1007, do remapping, and present a
different disk geometry to the system.  Thus, as far as the system is
concerned the disk *is* less than 1024 cylinders.

As a practical matter, if you use a reasonable disk divvy, you generally
aren't going to have filesystems this large.

Oh yeah, why are we talking about unix in comp.unix.xenix.sco anyway?
-- 
Chip Rosenthal  <chip at chinacat.Unicom.COM>
Unicom Systems Development, 512-482-8260 
Our motto is:  We never say, "But it works with DOS."