19 Apr
1999
19 Apr
'99
4:32 a.m.
The mode in which the Shugart SA1400 controllers, after which some of
XEBEC's controllers were patterned, was this ultra-simple model. That may
not have been the only mode, but I've got an 8" drive controller which seems
to work in this way, as it also has no device address switch. I've never
found the identifying logo or whatever, but the S-100 adapter I got with
this setup has a PROM marked "SA1400."
I've also read about this single-target-single initiator mode in the early
papers we used in establishing the SCSI-I standard back in the mid-1980's.
( I had the "privilege" of sitting through a number of the standards
committee meetings on behalf of my employer back then) Clearly, SOME makers
had used this as an operating mode. Multiple disk drives were not that
common among small systems back in those days.
Dick
-----Original Message-----
From: Eric Smith <eric(a)brouhaha.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Monday, April 19, 1999 12:07 AM
Subject: Re: Ancient disk controllers
> SASI, incidentally was essentially a
> Single-Target-Single-Initiator SCSI so it wouldn't need a device ID
switch.
SASI supported eight targets. Since there was only one initiator and no
disconnects, the initiator didn't need an ID. But the target devices still
needed IDs.
SCSI-1 added arbitration (for multiple initiators), disconnects (and
reselection), and the 10-byte commands (to support larger devices). I'm
not
sure whether SASI supported the message phase; that may
also be a SCSI-1
innovation.
Usually a SASI host can deal with SCSI disk drives. Sometimes a SCSI
host can deal with SASI targets, as long as it restricts itself to the
SASI commands.