[vcf-midatlantic] Steve Dompier's coding...

Herb Johnson hjohnson at retrotechnology.info
Fri May 6 10:05:57 EDT 2016

Thanks to Bill Sudbrink for starting this thread, and to other 
participants for their response and encouragements for some kind of 
"lecture" on this subject. Bill notes he got questions about 
IMSAI/Altair front panels. I'm often asked, why are S-100 cards so big? 
Why the "ugly boxes of big boards"? It's all related.

As I see it, I'd talk about how early microcomputing (1970's, pre and 
early CP/M era) was mostly what I'd call "resource scarce". The contrast 
would be post IBM-PC, certainly 1990's, I'd call "resource adequate", 
and later "resource rich".

In the early 70's, everything was expensive in terms of then-current 
income, and then-current technology. Memory. Circuit boards - big, to 
hold all the TTL chips needed. Low speed of processors. Speed and real 
cost of storage and display. And 100 pins? Sort of circumstantial, but 
it's a way to bring out all the decoded 8080 lines and features, so 
other cards didn't need to decode them, and to manage a front panel.

As Dave McGuire and others pointed out, front-panels were necessary as 
I/O devices; "storage" was pencil and paper as others noted. Good work 
could be done, as writing 1K or 2K or 4K programs was well within the 
capacity of one person, working in his/her head, in octal (or hex, or 
binary).  (I have modern examples of this, in 1802 coding.)

But, once there were ROM monitors, terminals or text-video, and some 
mass storage (cassette and diskettes), a front panel was an extra 
expense, time consuming, complicated. It went away. The Ithaca 
Intersystem DPS-1 I exhibited, across from Bill's Cyclops display, was 
the last S-100 front-panel system (I think), produced in 1980.


Herbert R. Johnson,  New Jersey USA
http://www.retrotechnology.com OR .net
preservation of 1970's computing
email: hjohnson AAT retrotechnology DOTT com
alternate: herbjohnson ATT retrotechnology DOTT info

More information about the vcf-midatlantic mailing list