MITS 8800B CPU Board

Allison ajp166 at
Mon Jun 13 19:44:14 CDT 2005

>Subject: Re: MITS 8800B CPU Board
>   From: "Dwight K. Elvey" <dwight.elvey at>
>   Date: Mon, 13 Jun 2005 17:12:04 -0700 (PDT)
>     To: cctalk at
>>From: "river" <river at>
>>Thanks for your replies. I found the relevant information.
>>I have an extensive inventory and can source the parts and get this poor, 
>battered board back to its old self again. However, looking through the doco I 
>noticed that the 8800B requires a display/control and interface boards. A 
>question for those of you that own a MITS8800 - does it need those boards for a 
>turnkey system? Can I plug the CPU board into the backplane and run it without 
>the d/c and i/f cards, assuming I set up the ROM and RAM cards for the system? 
>If not, (since I do not have the d/c and i/f cards) I'll have to try and build 
>them from the cct diagrams I have obtained. This is do-able (but a lot of work) 
>if I can get my hands on some blank S100 w/wrap boards, but I noticed there's a 
>1702 EPROM chip and I'd need to get the memory map for this chip to burn my own.
>>Failing that, and it's all too hard and bothersome for me, is there anyone that 
>would need a repaired 8800 CPU card for trade or anything similar?
> It should work on a turnkey. Almost everything goes
>through the S100 bus. Only the direct connect of the
>data bus goes directly between the panel and the CPU board.
>I don't think that is needed. You will have to have code
>residing at address 0000. This is not common. Most
>expected a working front panel that could load a boot
> Some ROM boards have a way to be at 0000 after reset
>and then switch to someplace else once things are booted.
> Don't give up on it. When there is a will, there will
>be a way.

Yes, you will have to have rom at 0000h though and Mwrite
was derived and delivered from the front pannel if memory
serves.  So that means ram will have to be set up to not
require Mwrite.  Either that or you will have to through 
something small together to create Mwrite.

As to mapping rom out once operational, thats a later problem.
It's fairly easy to do.


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