Re: SBC 80/20 Multibus

On Wed, 11 Mar 2009 21:34:31 -0400 mlawson <> wrote
in Message id: <>:

>Does anyone know of any SBC 80/20 Multibus card documentation or parts
>are available anywhere? Mike

Damn, I thought I might still have that one, but no. All I have is iSBX
specification, Multibus specification, SBX311, 86/14/, 86/30, and 86/12
manuals. You might try here:
http://www.retrotechnology.com/herbs_stuff/aubert.html

As for parts, what are you looking for?

On Mar 12, 10:25*pm, mlawson <blue...@embarqmail.com> wrote:
> What I'd like to find are some schematics, along with some working
> boards and motherboards. There are several sites that have .pdf files of
> the documents for S-100 parts, and I am hoping there are the same things
> for the multibus architecture.

S-100 and iBus are completely different except for their common
factor - the 8080 signalling standards. I believe I have 80-10
documents buried somewhere. A better answer comes with more
information on what you want to accomplish.

Another suggested it needed -12 volts. I believe it also needed -5
volts. The multibus also had to provide other essential functions
including power on reset and watchdog timing.

On Mar 14, 5:01*pm, mlawson <blue...@embarqmail.com> wrote:
> What I want to accomplish is to homebrew one. Many years ago I
> wirewrapped a TRS Model 1 PC and had a blast. Yep, I'm an old fart! And
> it's a nice little hobby. I'll probably re-configure it to support a
> Z-80.

Now I am completely inspired. Somebody who actually wants to learn
something rather than shotgun computer boards and call himself
knowledgeable.

Unfortunately, the hardware configurations of the Z-80 and 8080 are
different. And the Z-80 had a slightly larger instruction set.
Closer to the Z-80 was the 8085. I also designed hardware and wrote
software for that computer chip.

Because I am inspired, I dug through those piles from history. I
found multibus manuals for the 80/10 (8080 microprocessor) and 80/24
(an 8085 micro).

8085 was closer to the Z-80 (including no -5 volts required). But
Intel never got that chip to work fully correct. However Intel also
realized that the 8085 was wasting time playing catchup with the
superior Z-80. So Intel jumped forward to promoting the
simultaneously developed 8086 - which became the basis of what?

Zilog never recovered by trying to promote Z-80. Eventually Zilog
became part of Exxon when Exxon was foolishly doing what business
school graduates recommend. Z-80 was the first of many companies that
would attempt to challenge Intel's greatest power - its abilities to
innovate.

One neat feature of the 80/xx series were peripheral ports that
could be changed simply by replacing chips in 16 pin sockets. For
example, I reconfigured one design using especially powerful drivers
from Silicon Solid State Scientific (if I remember) that were more
powerful and transient hardened AND that were pin for pin compatible
with TTL chips for those sockets.

If I remember correctly, those multibus cards required better
regulation on its power supply as well as a master reset provided by a
multibus one backplane.

Eprom - largest was a 2732 on 80/10 and 2764 on 80/24. But again,
for memories over twenty years ago. Eproms from that other computer
would not work. Code must first setup peripherals unique to the
Multibus card. For example, Intel used its own serial port chip.
Many computers used a better (and different) serial port chip. Setup
required different bytes in different registers. Not that I am trying
to discourage you. But those multibus cards require writing code and
burn those newly programmed Eproms.