Unix, drive-types & Rom

[Ken Chapin]

In article <222 at wa3wbu.UUCP> john at wa3wbu.UUCP (John Gayman) writes:
>
>    How does Unix such as Microport handle hard disks that aren't listed
>  in the Rom disk table ?  Is it possible to utilize a drive for which
>  you have no Rom listing assuming you know all its parameters ?
>

We first look into CMOS to see what is configured. If the installer says that 
geometry of the drive is different from what CMOS says, we write out the new
geometry in the pdinfo block (see /usr/include/sys/vtoc.h) that sits on a 
reserved location of the disk. That reserved location is by the way on the first
sector of the second track of the drive. By putting the pdinfo table there, you
don't have to know the exact geometry of the drive before you write (like know-
ing the number of sectors per track). You just have to assume that the drive has
got at least two tracks.

Ken Chapin         UUCP: ...!{sun | ucbvax | ihnp4}!amdcad!uport!ken
Microport Systems
Technical Support