[960] in linux-scsi channel archive
Re: Adaptec -> NCR
daemon@ATHENA.MIT.EDU (Leonard N. Zubkoff)
Sun Nov 17 15:54:59 1996
Date: Sun, 17 Nov 1996 12:48:53 -0800
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: groudier@club-internet.fr
CC: stephen@it.com.au, linux-scsi@vger.rutgers.edu
In-reply-to: <Pine.LNX.3.91.961117211109.166A-100000@localhost> (message from
Gerard Roudier on Sun, 17 Nov 1996 22:00:01 +0000 (GMT))
Date: Sun, 17 Nov 1996 22:00:01 +0000 (GMT)
From: Gerard Roudier <groudier@club-internet.fr>
I am sure that the aha1542 driver of linux, at least until some 2.0.X
revision does not probe correctly "extended BIOS translation" option for
1542CF controllers.
How can the BT-948 guess?
Does it assume that user has set "extentend translation" for disks
capacities >1024x64x32 sectors?
My opinion is the following:
- linux ncr drivers use scsicam_bios_param() (drivers/scsi/scsicam.c).
This function first tries to infer mapping from partition table. If that
fails, it tries to apply SCSI2-CAM (X3T9 / 792D) etc... in order to
assign a disk mapping in tracks, heads, sectors.
- linux buslogic driver does some reverse engeniering of adaptec propriatary
bioses to choose disk mapping.
So, it is possible that users who used old adaptec controllers will
be more fortunate with BusLogic driver.
However, if drives have more than 1024x64x32 sectors they can have
problems too.
There's no reverse engineering involved. BusLogic's own BIOS uses three
translations, 64/32, 128/32, and 255/63. If it finds one of those already
present in the partition table, it will adopt and use the existing one, and
ignore ths setting on the > 1GB disk translation switch in AutoSCSI. Since the
Adaptec only uses 64/32 and 255/63 translations, which are a subset of the
BusLogic ones, any disk formatted/fdisk'ed on an Adaptec should work, though it
may lead to a warning from the driver that the partition table geometry does
not match the setting of the > 1GB switch.
Leonard
