[vcf-midatlantic] changing my bus route

Herb Johnson hjohnson at retrotechnology.info
Thu Jan 13 20:18:38 UTC 2022

[A lot of old-school tech chatter today!]

Discussion of Multibus vs S-100 bus

Joe apparently missed both Jeff's message about retrobrew computers, and 
my message on auction-site prices for S-100 boards. On price S-100 
boards will be cheaper than Multibus (except collectables). I imagine 
he's caught up now.

And a S-100 board of 5 X 10 inches is an awful lot of space. Multibus is 
about 6 X 12: whadda gonna do with either size? It's a lot of chips, 
especially modern chips.

Jonathan makes the point: do something with something, then see where 
you go next. You don't have to start with your destination design, in 
fact it's advisable to start simpler and make your mistakes early.

I'm relatively active in vintage Multibus. Certainly enough to agree 
with Jonathan Chapman's assessment of Multibus. It's a little more 
complicated than S-100 and IEEE-696. It can get a lot MORE complicated 
because these were used in complex industrial settings and industrial 
products (as were some S-100 systems).

As David Guesswein suggests, there's not widespread vintage interests in 
Multibus, as those who worked on Multibus have aged-out of the vintage 
computing discussion. Also Multibus was an industrial product, whereas 
S-100 was both industrial and popular-computing in its lifetime. 
Essentially S-100 was the cheaper alternative to Multibus.

Today there's a somewhat private Google group who have revived 
Intel-based Multibus development systems.


Otherwise a Web search may find various Multibus pages and sites with 
information (including mine). I'm not aware of all that many, but i 
don't engage much with many online discussion groups. If you find more 
activity online about Multibus, let me know!

So discussion about Multibus that I'm aware of, quickly becomes 
discussions with engineers of decades of experience in programming or 
hardware design, about fairly busy systems that performed control or ran 
20th century operating systems. I get intimidated, and I know some stuff.

But the early bussed stuff - Multibus or S-100 bus or say STDbus - is 
approachable for the technically minded. Jon Chapman has revived the old 
OSI bussed systems and one 8080 multibus board. There's SWTPC, the SS-50 
bus, with some revived new boards by corshamtech.com, that's a 6800 6809 
classic bus. Busses get more obscure from there.

There's many points of entry, for people who want to design up something 
at the vintage processor-chip level. and for each kind of "entry", 
there's of course people who have been there and know what's went on. 
But some of these are pretty complicated and busy, with lots of legacy 
stuff that can be intimidating or simply not of interest. Others are 
simpler: the single-board stuff was intended to be simpler and 

As I and others said: Joe, where you start may not be where you end up. 
There's good reason to make a few simpler things first, then more 
complicated things later. from the experience of doing so, you'll know 
what to look for and what's of interest to you in the next step.

Put another way: I've had lots of people contact me (I have some 
reputation in the S-100 world) about their "ultimate S-100 system" who 
never got there. One reason may be, they didn't get enough prior 
experience on simpler systems or projects, and so were not able to "get 
traction" on critical S-100 concepts or complexities or about CP/M (the 
predominant OS for S-100). So they gave up.

Regards, Herb Johnson

Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT comcast DOT net

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