11 May
2007
11 May
'07
5:04 p.m.
I've posted a photo of my Microcomputer Systems Corporation SA4000-to-
GPIB disk controller PCB here:
http://www.sydex.com/durango/msc1088.jpg
This is a large board (12"x19")that contains mostly 74LSxx logic.
The two 24-pin cerdip packages at the top left side are AM2506DC 4-
bit ALUs; the 28-pin package below them is a N8209 (Signetics) 64x9
bipolar RAM. The 40 pin package to the left of them is an Intel 8291
GPIB talker/listener. The
Just thought I'd snap a photo before it went back into its box. The
documentation for the board (just command definitions) is dated 1979.
FWIW,
Chuck
11 May
11 May
7:59 p.m.
Chuck Guzis wrote:
I've posted a photo of my Microcomputer Systems
Corporation SA4000-to-
GPIB disk controller PCB here:
http://www.sydex.com/durango/msc1088.jpg
This is a large board (12"x19")that contains mostly 74LSxx logic.
The two 24-pin cerdip packages at the top left side are AM2506DC 4-
bit ALUs; the 28-pin package below them is a N8209 (Signetics) 64x9
bipolar RAM. The 40 pin package to the left of them is an Intel 8291
GPIB talker/listener. The
Just thought I'd snap a photo before it went back into its box. The
documentation for the board (just command definitions) is dated 1979.
FWIW,
Chuck
MSC if I recall correctly morphed into Xebec, who was one of the first
if not the first supplieres ot controllers to IBM for the XT.
The did make several controller adapters which allowed Microdata to
hook up both SMD and 2314 type drives with RF data to our mini
computers. They had 25mb drives, which were ISS. Later they
made a controller for the Microdata reflex which was supposed to
be SMD, but had a flaw in the write splice that made it incompatable,
with SMD design. They refused to fix this since it made others
unable to sell drives to go on the systems they sold.
I guess this controller probably falls in the gap between the
minicomputer days, and the micro days of the XT.
It would be interesting to have a family tree for this part
of the industry, from the company standpoint as well as
the people standpoint. A lot of companies had engineers
depart and found other storage business companies, and
I'm sure MSC / Xebec must have been one.
jim
9:29 p.m.
On 11 May 2007 at 19:59, jim wrote:
MSC if I recall correctly morphed into Xebec, who was
one of the first
if not the first supplieres ot controllers to IBM for the XT.
I believe that's true. I remember going over to their "incubator"
offices off of Mathilda (IIRC) and talking with them about this
board. I think they also did tape controller work. As I mentioned,
I have the programming spec--it's a longhand-edited version of their
stock MSC-1000 controller docs. I have the feeling that they did
quite a few "custom" jobs back then, mostly modifying the host-to-
controller part to order. Note the many empty DIP positions on the
left (host) side of the controller. Also not that there are 2 20-
position drive connectors on either side of the 50-position connector
on the right side of the board. We didn't ask for the 2nd drive
capability and couldn't have used it anyway. Within 2 years, the
5.25" hard drives started making their appearance and we went to a
controller card using bipolar 8X300 logic that was the size of an S-
100 card. Things moved very fast back then.
Sometime between this unit and the XT controller, I think they went
to programmable bit-slice components for their controllers (8X300?
2901?). This one's interesting in that, with the exception of the
8291, it's all discrete logic; no big ROMs or LSI.
Cheers,
Chuck
12 May
12 May
11:14 a.m.
Chuck Guzis wrote:
On 11 May 2007 at 19:59, jim wrote:
The controller that Microdata had was modified from the controller design
that ran Microdata branded drives directly, but was also all 7400 logic with
a 74181 alu type cpu sequencer. I have schematics for both versions of this
that hopefully will get scanned and posted on bitsavers sometime soon.
Microdata's cpus were both ALU type cpus while I was there in the late
70's and the controllers all had 1 or 2 in their sequencers as well, in
their
disk controllers, and in their terminals. Tape and com controllers were
more state machine type devices, and the printer, card reader, and
paper tape read punch boards were just parallel access interfaces
with the cpu doing the work.
Was the back end of this controller anything resembling sasi, sequential
or parallel register interface? I think the MSC controllers into the
microdata minis were all serial interfaced on the back end, since
the controller cabling and logic had RF serial / deserializer logic
that had to remain, since they talked to both microdata drives which
were serial RF as well as the MSC controllers w/o any extra
connectors to go around the serial logic.
you moved a jumper or two, but other than that, the MSC controller
just made more heads and cylinders show up to the software, and
the seeks were also passed as pulse trains, not as parallel
info (like SMD).
Xebec picked up and modifed the SASI interface and blessed us
with a fouled up early SASI command set which survives at the
heart of IDE of course. I'm not aware of a "Xebec" or "MSC"
design that survived, but just as you say a lot of custom adaptations.
Jim
MSC if I recall correctly morphed into Xebec, who
was one of the first
if not the first supplieres ot controllers to IBM for the XT.
<snip>
Sometime between this unit and the XT controller, I think they went
to programmable bit-slice components for their controllers (8X300?
2901?). This one's interesting in that, with the exception of the
8291, it's all discrete logic; no big ROMs or LSI.
1:07 p.m.
On 12 May 2007 at 11:14, jim wrote:
Was the back end of this controller anything
resembling sasi, sequential
or parallel register interface? I think the MSC controllers into the
microdata minis were all serial interfaced on the back end, since
the controller cabling and logic had RF serial / deserializer logic
that had to remain, since they talked to both microdata drives which
were serial RF as well as the MSC controllers w/o any extra
connectors to go around the serial logic.
This one is GPIB-to-SA4000 (MFM-ish, but with an on-board data
separator and fixed-head byte clock). There's a DIP switch on the
board for the type of drive (SA4004=14MB, SA4008=30MB),
listener/talker ID, and presence/absence of a fixed head track.
Xebec picked up and modifed the SASI interface and
blessed us
with a fouled up early SASI command set which survives at the
heart of IDE of course. I'm not aware of a "Xebec" or "MSC"
design that survived, but just as you say a lot of custom adaptations.
This one seems to follow the convention for HPIB disk drives, with a
few flags and commands added.
I've got an Ampex ISA SASI interface card somewhere in my hellbox.
As near as I can tell, it was used to connect with a box containing a
QIC tape drive and a hard disk on a PC. Nothing exciting on the card-
-just random logic for the parallel interface and a BIOS ROM.
Cheers,
Chuck
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