2 hardrives of different interfaces allowed to coexist in PC UNIX?

[Doug Pintar]

In article <25 at opel.COM> johnk at opel.COM (John Kennedy) writes:
>
>I agree.  The documentation and menus indicate you can set up a primary ST-506
>and a secondary SCSI, but what I tried was the opposite:  having an old ST-506
>controller and drive available as secondary.  My attempts, too, failed.
>
>Anyone had any luck with this?  Followups to comp.unix.i386.

There are some problems trying this.  For MFM controllers, the way you get the
geometry of the drive is usually from drive-type entries in the CMOS RAM.
Since you have to tell your system that you have NO 'AT-style' hard drives
to get a SCSI adapter to boot from one of its disks, this leaves the driver
in the dark as to what the drives on the MFM controller look like.  For ESDI
it's no problem, as you can get the geometry from the drive (unless you used
some bizarre controller translation mode when the filesystems on it were
built).  Adaptec pulled a hacko in their RLL controller to record a couple
bits of the configuration in each sector header for the first few tracks of
cylinder 0.  Must have been some INTERESTING microcode that was run when you
asked the controller for the config info...  Anyway, there's supposed to be
an IOCTL to pass both the physical and apparent geometries of drives so that
you could have some sort of init program that did this prior to opening them
the first time, but it's unclear whether it actually works.  I tried it once
with no success (on a beta 2.2 system) and haven't messed with it since.  It
may have gotten fixed since I tried it.  Good luck,
DLP