<One of the problems with the S100 bus is that it is _very_ dependant on
<the 8080 signals. Even using a Z80 is a bit of work - things like PINTE
<(which indicates if interrupts are enabled) and SSTACK (address lines
Neithrr of which had much application.
<Actually, I prefer the Motorola / PDP11 idea of having memory and I/O in
<the same address space. It means you can use the same instructions and
<addressing modes to access either.
nothing about z80, 8085 or 8088 stops one from doing that. The Northstar*
floppy controller was memory mapped for exactly that reason.
Allison
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, 30 March 1999 6:43
Subject: Re: Decwriter II
>The paper out logic is pretty simple. The output of the switches goes
>through a little RC circuit to the input of a 7474 d-type (unfortunately
>which chip this is depends on the board version - it's E5b on an M7723
>and E34b on an M7728). The output of that ff is the ready line.
marvin was kind enough to post similar data. Looking at that area this
afternoon.
>It appears that the switch is closed when the printer is out of paper. So
>my first test would be to find the 100 Ohm resistor between the D-input
>of that chip (pin 12) and pin BB on the keyboard connector. Unsolder it.
>This disconnects all the switches. Does it work now?
No.
>I don't, alas, have the schematic of the chassis. But it appears from a
>general wiring diagram that the paper out switch is in parallel with the
>cover interlock switch. Have you checked that one?
Yes. the switches are not implicated. I disconnected the whole switch
assembly, still no go. Stuck output on the chip I'll bet, the fact it was
intermittent for a while makes a logic chip failure even more likely. (I
don't think I mentioned that earlier)
Thanks for your help......
Cheer
Geoff Roberts
Hi,
I have some DEC cables that I peicked up. Does anyone know what they're
for?
Marked "BC-022D-10" also "82351-000" DB-25F on both ends estimate 10
foot long
Marked "BC22D-50" also "71065" DB-25F on both ends, estimate 50 foot long
Marked "BC22D-25" also "71065" DB-25F on both ends, estimate 25 foot
long,NIB
Thanks,
Joe
Thanks for posting this information. It might be useful, in addition, at
least to me, to have to correspondence with the S-100 bus pins so they can
be cross-referenced to the '696 standard signal names. I do hve the 8080
data in house, but nothing tying it to the S-100 bus pinout or timing.
Actually, it might be as correct to say that 8088 signal names are more or
less like "all the other" microcomputers in the non-Motorola camp. with the
8085 and z-80, it became obvious that the large number of strange signals
generated by the 8080 didn't even help the Intel folks with the task of
interfacing the processor to memory and peripheral devices. The simple
interface used by the 8085 and Z-80, which had to be painstakingly created
>from an 8080, lives on, in the ISA and other bus architectures. What it's
come down to over the last 20 years is that you need a pair of signals, i.e.
nRD and nWR to tell you (1) that something's going on, and (2) whether it's
a transfer of data to or from the processor. Additionally, it's nice to
know whether the read or write is between the processor and memory or I/O.
With the MOT class of processor, you have an address strobe to tell you a
cycle's begun, and you have to decode the address to determine whether it's
I/O space or memory that's the target. In either case, you need only one
level of logic to create the necessary strobes, and none of it is clocked
logic, so no nonessential time loss is generated.
One of the reasons the S-100 required such fast memory for its relatively
slow processors was that you had to operate relatively complex timing
structures to create proper timing. That's a reason the standard, in my
considered opinion, killed the S-100 rather than perpetuating it. Intel
figured this stuff out a decade earlier with its Multibus-I. That used a
very ISA-like set of bus handshakes. Because the '696 standards committee
couldn't take the hint from the rest of the world and simply pick WHICH
write signal to use and WHICH read signal to use and that they couldn't
figure out that the system didn't need to have data valid at the beginning
of a write cycle, but only a short while before the end, and that data had
to be held for a time after the end of a cycle, simply was a dreadful shame.
That's what happens when folks meet with no intention of compromising. The
result of course, was the chaos that results when surplus vendors e.g.
CompuPro/Godbout (cited here because they were BIG, not because they were
BAD) design their boards considering only what's out in the dozen 55-gal
drums full of TTL parts in the warehouse as opposed to how the functions can
be implemented BEST.
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Monday, March 29, 1999 2:18 PM
Subject: Re: Rebirth of IMSAI
>>
>> GAWD! The 8080 data sheet! I wonder if my archives go back that far . .
.
>
>
>I know I still have the 8080 data sheet (actually a NatSemi version of
>it). I found it the other day when looking for the SC/MP data (which I
>also found...)
>
>> Soooo . . . the signals were named the same also, eh? pSYNC, /pWR,
sMEMR,
>> etc???
>
>I have the Imsai 8080 CPU board schematics here.
>
>Here are the signals (modulo buffering/inverting):
>
>reset/ -> 8224 clock generator reset
>Prdy, Xrdy logically ORed and fed to 8224 rdyin
>PINT/ -> 8080 INT
>HOLD/ latched by D-type (clocked from phi2), -> 8080 Hold
>POC <- 8224 reset output
>Phi1 <- levelshifted 8224 phi1 output
>SSW DIS/ -> logic -> data buffer enable pins
>Phi2 <- 8224 phi2ttl output
>Cloc <- gate-delayed version of phi2
>Data, address lines <- 8080
>Pwait, Pwr/, Pdbin, Pinte, Phlda, Psync <- 8080
>CCDSBL -> enable line on buffers for last list of signals.
>Addr disbl/ ditto for address buffers
>DO Disbl/ ditto for data out buffers
>RUN, SS -> logic -> data buffer control
>SINTA, SWO, SSTACK, SHLTA, SOUT, SM1, SINP, SMEMR <- 8212 latch on CPU
>data lines, clocked by STSTB from 8224.
>STAT DISBL -> enable of buffers for those lines.
>
>That#'s basically it. The S100 bus is very similar to the raw 8080 lines
>(like 8-bit ISA is pretty much 8088 signals).
>
>-tony
>
At 09:27 PM 3/29/99 -0800, Sellam wrote:
>Same difference. [110 baud vs 110 bps ]
Bzzzt! And thanks for playing. Actually this would be a reasonably good
trivia question. The term 'baud' is used to indicate signalling states, the
term 'bits' is used to represent transmitted data. The ASR-33 transmits 110
signaling states (bauds) per second, out of every 11 one is a start bit,
eight are data bits, and two are stop bits, thus the number of bits per
second is actually 8/11 * 110 or 80 bits per second. When you use 8 bits to
represent a character this is 10 characters per second.
--Chuck
Today I went to see a couple of the people that I meet at yesterday's
hamfest. One of them used to service XEROX computers. He told me that he
threw out three rooms full of old XEROX computers less than a year ago. :-(
He gave me part of the stuff that he had left, I have to take a Truck
(note capital) back to get the rest (estimated at two cubic yards but no
complete machines). So far I've found lots of docs and 8" flopppy disks
for the 820 and 16/8. The 16/8 looks pretty interesting, it ran CPM,
CPM-86 and MS-DOS. Does anyone have one of these? What's your opinion of
them?
He has a floppy disk drive control box to manual operate 3.5", 5.25" and
8" drives during alignment. Anyone have an idea of what one of these is
worth with the alignment disks and manuals?
Alos found a Lisa mouse to go with the Lisa that I got yesterday.
Joe
I have been offered a "Vector Graphic B" and would like to find some more
information about it. I have found they did a 1 and 1+ from the Haddock
book and I have seen reference to an "MZ" on the comprehensive computer
catalogue. Where there other machines in their range? The "B" apparently
runs the p-system was this common for these machines or did they run any
other systems? I would like to talk to any other collectors out there who
have one of these machines so I can work out just what I will be getting.
Many Thanks
--
Kevan
Collector of old computers: http://www.heydon.org/kevan/collection/
OK, this is totally off topic, but if you haven't heard the weekends news
I'd recommend checking out the following URL:
http://www.zdnet.com/zdnn/special/melissavirus.html
Normally I discount these as hoaxes, but this isn't. Thankfully I'm one of
the 'Dinosaurs' at work that refuses to give up an antique RS/6000 for a
nice shiny new NT box, so I'm still on UNIX e-mail.
The problem in a nutshell, don't open any messages in a Microsoft E-Mail
program with the following title "Important Message From: {persons name}".
Zane
| Zane H. Healy | UNIX Systems Adminstrator |
| healyzh(a)aracnet.com (primary) | Linux Enthusiast |
| healyzh(a)holonet.net (alternate) | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| and Zane's Computer Museum. |
| http://www.dragonfire.net/~healyzh/ |
Anyone know where I'd find a circuit diagram for a Decwriter II?
Preferably in South Australia.
I have one that thinks it's permanantly out of paper.
(No, it doesn't seem to be a microswitch)
I suspect it's just a stuck logic state in a 74xx ttl chip, but a circuit
will make it a lot easier to find.....
Alternatively, if this is a common fault, anyone know which chip is
implicated?
Cheers
Geoff Roberts
Computer Systems Manager
Saint Mark's College
Port Pirie, South Australia.
Email: geoffrob(a)stmarks.pp.catholic.edu.au
ICQ #: 1970476
Phone: 61-8-8633-8834
Mobile: 61-411-623-978
Fax: 61-8-8633-0104
At 08:37 PM 3/29/99 -0800, Sellam wrote:
>
>Does anyone know what the function of an IBM 557 Alphabetic Interpreter
>is/was?
... and yes, if you had not guessed... I still have a manual on how to
program these things!
(now, if I could just remember that trick that we used to teach a 402
tabulator how to multiply... B^} )
-jim
---
jimw(a)agora.rdrop.com
The Computer Garage - http://www.rdrop.com/~jimw
Computer Garage Fax - (503) 646-0174
