MITS8800 CPU Board

Allison ajp166 at
Tue Jun 14 05:50:08 CDT 2005

>Subject: MITS8800 CPU Board
>   From: "river" <river at>
>   Date: Tue, 14 Jun 2005 16:23:21 +1000
>     To: <cctalk at>
>Great, thanks for the info.
>I'm sourcing a few S100 protoboards, so I'll be able to wirewrap a board with all the relevant RAM, ROM and I/O. I'll probably use later generation chips such as 62256 for RAM and 6264 for ROM. I can then put in the 8251 and 8255 for serial and parallel ports, respectively. Is that heresy in regards to these old boards?
>It's not an issue to me starting ROM at 0000h. I've written a few 8080 
>I've only got a 6-slot motherboard and a Northstar ZCB processor board, 
S100 ROM board and some Dynabyte RAM boards and I was going to use the 
motherboard and original S100 boards with this system.  

This means the 8800CPU board will be in a small 2-slot system - the CPU board and the RAM/ROM/IO board I'm going to make.

The NS* ZCB has a power on jump (POJ) and reset logic so you dont need 
rom at Zero plus it also generates Mwrite.  Besides being Z80 it's a 
better CPU to use.

>Just one more thing.... I suppose it's possible to use the 8800CPU bd 
>without the power regulation components if I ensure the correct 
voltages go through the correct pins on the bus. I can then use an 
old spare PC power supply, instead of creating a new supply. Naturally, 
this would entail that no other S100 board can be used due to their 
on-board regulators. This isn't an issue if I build my own S100 boards, 
without regulation, for this system.

You can add regulation a trivial thing.  However using a PC supply is 
fine (you'll need -5 -12 +5 +12).  Regular S100 cards can be used if 
you bypass the regulators.

>Again, thanks for your help. This is my first foray into S100 stuff, 
and makes a nice change from Multibus.

Nice change?!?  You will be messing with hardware much more.  S100 
you'll find there are a few quirks like noisy backplanes and cards
that are S100 but not always compatable with the CPU in use.


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