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Re: [N8VEM-S100:1758] IMSAI 8080 CPU card replacement

Hi John,
  That would definitely be the ideal situation for machines with front panels like the IMSAI & Altair.  I, for instance, have 2 IMSAI chassis's but don't have an 8080 CPU board to go with them.  I looked at the original design of Josh's as a good way to demo the IMSAI and play with front panel operation.  I have obtained 2 Cromemco ZPU boards which support the front panel but I admit that I would also like a 8080 board for these machines.  At some point I also would like to demo loading Microsoft 4k Basic from paper tape and as far as I know Altair 4k tape Basic will not run on a Z-80  because of the differences in how the 8080 & Z-80 handle the parity flag.  If an 8080 replacement board is created which has full access to the bus, it would be fantastic.  Unfortunately, I have no background in design so I would be very grateful with anything that can be done in this area.
Jeff Galinat

On 8/7/2013 1:16 PM, John Monahan wrote:

Guys, I’m wondering if it would make sense to modify that board more. I see there is a decent demand for it.  If people are not in a hurry it might make sense to modify it could act as a bus master like the old style IMSAI/Altair accepting DMA etc.  This would require adding a  true data bus  in and out lines, 2MH clock etc. so it could actually be used with other S100 cards in the bus.


I (or others), could take a stab at this, but it probably would be best to do a prototype board first.


Comments welcome.





John Monahan Ph.D

e-mail: mon...@vitasoft.org

Text:    mon...@txt.att.net