[vcf-midatlantic] First homebrew computer project

Jonathan Chapman lists at glitchwrks.com
Sun Jan 2 01:42:15 UTC 2022

> My current inventory of MCS-80 components:
> C8080A CPU (gold/white)
> P8212 8-bit I/O port
> C8214 priority interrupt control (gold/white)
> (2) D8216 4-bit bi-directional bus driver
> D8228 system controller & bus driver
> (2) D8238 system controller & bus driver
> C8255 programmable peripheral interface (gold/white)
> (3) C2112A 256x1 bit SRAM (gold/white)

Looks like you about have the contents of the SDK-80 starter kit!

> I'm sure I'm probably missing one or two crucial support chips.

Just the 8224 clock generator, which is pretty important -- it's a hassle to do it without. Let me know if you need one, I have several NOS parts and around 300x Soviet clones (which run cooler anyway).

> I'll definitely need a bunch of a much higher capacity RAM, since 96 bytes just doesn't seem like enough. I'm pretty sure I have a ton of SRAM chips of more reasonable capacity but I just have to dig them out. Same goes for EPROMS

Realistically it makes the most sense to go with a 2716 EPROM or newer, as there are usually drop-in EEPROM options, and you can program with even modern-ish programmers. Plus they're typically 5V only after that point, except for some sort of oddball TI parts.

> As as far as construction and form factor, I was thinking about doing it on s100 prototype boards and a large backplane so that I could add commercially built cards to the system.

You probably want to actually do S-100 then, there are better backplane/connector options if you're not actually going to implement S-100 bus. Plus, as you say, that opens you up to a ton of ready made cards!

> I might eventually want to add a floppy controller. I know it would probably make more sense to use some type of flash interface, but I want this machine to be configured as if it was built in the late seventies or early eighties.

Nothing wrong with floppies! That's mostly what I use.


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