The Adventures of a home brew 8Bit Computer

Got a few parts in such as the MC6800 and the 74s189 chips. For some odd reason I thought the 74s189 was a Static RAM chip. It’s not, it’s a Dynamic RAM. So now I need to find some proper Static RAM.

Also the 6821 chips I had in my junk box don’t work. I got these chips from a box of electronic parts from a friend when he went to ITT Tech and I have come across a few 74 series logic chips that are dead so it wasn’t a surprise the 6821 ICs were dead as well.

However this is great news so now I can go ahead and go with a z80 CPU. After all I bought ten z80420A PIO chips when I bought the 74s189 chips.

The overall form factor of the system is going to be a back plan with a CPU card, Memory/ROM card, video card and a general IO board. Maybe a switch console or parallel LCD. The video card will be the last item to build so I’ll mostly be using a serial terminal. I guess I should also find some z80 SIO chips to toss in as well. If I do that I will have the PIO, SIO and RTC on their own board.

I plan to wire wrap the computer boards but for the back plan I might etch a PCB or strip board it. Since the cards need to be inserted and removable wire wrapping the sockets on the back plan would be a back idea. I would love to use the old ISA style edge card design but the card edge sockets cost too much so I might just use double row or right angle single headers.

In all I don’t plan to try to do the smallest chip count or making it small as possible. I also don’t plan to build this overnight and expect it to work. This is going to be long-term project and once in a while chime in on here about the progress of it. The overall goal is to getting a standalone system up and running CP/M or MP/M.


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