S-100 Build

CyberBob

CyberBob

Member
I am going to start an S-100 build. This will be of interest to 8080 and Z80 fans. I already have a chassis that is the same or very similar to those used in the original Altair/IMSAI computers and is from the same era (I've had it for maybe 30yrs). Will bring it up from Socorro tomorrow. Original backplanes are stupid-expensive and rare, so will probably get a repro off eBay. May use a modern switcher for the power supply, TBD. Will also try for original boards but may go repro on some of those as well due to prices of original gear. Did pick up a sweet multi-function S-100 from Panhandle Bob on Thursday. Details on that board to follow.
 
The first board is a Micromation M/Net I/O with:
1. Four serial USART's (8251), individually selectable baud rates (150-9600 BPS)
2. 50-pin parallel port with two 67S374 output drivers & an 8255 Parallel Peripheral Interface
3. 8253 Programmable interval timer
4. 5832 Time-of-day clock with battery back up
 

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  • Microimation MNet.jpg
    Microimation MNet.jpg
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My Altair/IMSAI-style chassis for this project. It's been in storage for maybe 30yrs.
 

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  • OldChassis.jpg
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An IMSAI chassis. Definitely had cooler switches. I should go for those switches in this project, but those standard toggles are what were on the TI and Data General computers I worked on back in the day.
 

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  • imsai2x.jpg
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Going to go Altair. Switches are cheaper, has its' roots in Albuquerque, and it's the older machine. Going Z80A instead of 8080 because Z80A has NMI and only needs +5V while 8080 needs +5V, -5V and +12V.

Just learned that the Altair front panel was modeled after the Data General Nova computers, which is just what I compared it to a few posts up ^^^.

Back to power, actually the S-100 standard requires +8V and +/-16V. Period boards rely on these higher voltages as they do onboard regulation. So, need to find a switcher that can be adjusted up to these values. As a 'for instance', a 7805 +5V linear regulator, which is used by most boards of the time, requires 7.5V to regulate 5V. (edited)
 
Backplane came out of the dishwasher squeaky-clean. Shoved the Micromation I/O board and a Hayes modem board into it for the vintage fest just for display. Gonna bring the chassis up from Socorro in a few days so I can start figuring out how to mount everything. Still need a CPU board, switch/indicator front panel, and a power supply.
 
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