30 Jun
2005
30 Jun
'05
1:17 p.m.
Subject: Re: SASI device <-> PC ?
From: Jules Richardson <julesrichardsonuk at yahoo.co.uk>
Date: Thu, 30 Jun 2005 19:45:19 +0000
To: cctalk at classiccmp.org
On Thu, 2005-06-30 at 12:14 -0700, Lyle Bickley wrote:
The deal is that SASI is almost SCSI.. the differences are very
small at the hardware level (interface). However the protocal and
instruction set of the SASI bridge controllers is different from
SCSI. That difference in instructions and protocal does not
allow for mixing the two nor simple substitution of one for the
other. SCSI was not standardized till the late 80s so there are
a number of SASI/SCSI devices that predate the widespread acceptance
of SCSI. There are a few systems that have a SCSI interface that
were SASI or SCSI subset (DEC uVAX2000 for one). I've also done
the reverse, used SCSI on older SASI machine but, it required a
new bios to even talk to the SCSI disk. The later was due to the
SCSI vs SASI bridge board (Xybec) instruction/protocal differences.
Allison
It's been a while since I used the
controller, but IIRC it was an old ISA
controller card like a WD7000 or Seagate ST-01/ST-02. Any early SCSI-1
controller should do - that was before SCSI became "smart" - and the
messaging between the controller and the device (HDD) was minimal. A SASI
device on such a controller will respond "well enough" to "look like"
SCSI-1.
As I said before - DO NOT mix a SASI device with a SCSI device on the same
controller - or strange things can happen (don't ask).
Yep - far as I remember, SASI's single target only, so I expect if you
have a SASI target on the same bus as a SCSI target all sorts of things
would happen! :-)
Most classic SASI controllers seem to be little more than a handful of
buffer and latch ICs though (only about 6 chips total) - hence I was
wondering if someone had chucked together something to hang off a PC
parallel port (and just drive it all in software). Not especially
complex - my worry would be that the SASI target would timeout on
certain ops if the PC parallel port isn't quick enough though.
cheers
Jules 
30 Jun
30 Jun
2:58 p.m.
On Thu, 2005-06-30 at 16:17 -0400, Allison wrote:
The deal is that SASI is almost SCSI.. the differences
are very
small at the hardware level (interface). However the protocal and
instruction set of the SASI bridge controllers is different from
SCSI.
Yep, they're close but not quite. Not sure if SASI supported ten-byte
commands either (probably not).
To further muddy the waters, there seems to have been a time where SCSI
was replacing SASI, but the SCSI Common Command Set wasn't yet ratified
- so things existed that were for all intents and purposes SCSI, but
left out a few commands here and there (some of the OMTI tape
controllers I seem to remember are like this).
Hence the reason I'd quite like a simple paralle-port type interface
than going the internal ISA card route as I expect I'd find there are
always going to be a few exceptions to the norm here and there that'll
need to be worked around - and it'd be easier to do all the driving in
user-land on a PC than messing around with hacking device drivers at any
kind of OS level...
cheers
Jules
7115
days inactive
7115
days old
1 comments
2 participants
participants (2)
-
ajp166＠bellatlantic.net -
julesrichardsonuk＠yahoo.co.uk