[964] in linux-scsi channel archive
Re: Adaptec -> NCR
daemon@ATHENA.MIT.EDU (Leonard N. Zubkoff)
Sun Nov 17 18:23:48 1996
Date: Sun, 17 Nov 1996 15:21:59 -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.3.91.961117232821.298A-100000@localhost> (message from
Gerard Roudier on Mon, 18 Nov 1996 00:34:22 +0000 (GMT))
Date: Mon, 18 Nov 1996 00:34:22 +0000 (GMT)
From: Gerard Roudier <groudier@club-internet.fr>
I am sorry Leonard. I was wrong about the reverse engineering from Adaptec.
I understand in your code that the driver reports only BusLogic translations:
64/32, 128/32 or 255/63, and obviously it is the right thing to do.
When existing partition table infers translation, Adaptec to
BusLogic compatibility can only be ok.
Otherwise, we only may have problems for capacities >= 2*1024*1024
and < 4*1024*1024 (1024 MB to 2048 MB).
Am I still wrong?
I'n not sure precisely what you're saying... Moving a disk from Adaptec to
BusLogic will always work, since the Adaptec translation set is a subset of the
BusLogic set, and the BusLogic BIOS will adopt. Moving a disk that's >= 1GB
and < 2GB from BusLogic to Adaptec won't be correct if it was formatted with
BusLogic's 128/32 translation. Personally, I always turn off the > 1GB switch
and create partitions with the 64/32 translation since it's the most common
across all SCSI host adapters.
My Atlas 2.1GB is translated 70/62 1015 sectors. NCR BIOS seems to
be quite happy of that. Fortunately I will continue with NCR controller
family.
Just one question:
Did Adaptec copy BusLogic BIOS mappings, or is it the opposite?
I really don't know for sure. Long, long ago, BusLogic's (then BusTek's) first
products were the BT-542B and BT-742A which were originally software compatible
with the Adaptec 1542. I think that many early SCSI host adapters used the
same 64/32 translation because it's pretty obvious and worked fine up to 1GB.
I don't know who first discovered the need for extended translation or
implemented it. The 255/63 translation is also pretty obvious, in my opinion,
since it's the largest possible. The existence of the 128/32 translation on
BusLogic makes me think that the designs were independent. Personally, I think
the 128/32 is unnecessary; it saves a little space, but isn't really worth the
trouble.
Leonard
