front panels

From: Allison J Parent <>
Date: Tue Feb 24 20:58:16 1998

<>> Processor. The 8080 CPU does I/O To/From the accumulator which is
<>I beg to differ.

Last I checked, today the 8080 IO is from and to the accumulator.

<>All you have to do is to put the CPU into a wait state, tri-state the
<>bus buffers and directly drive the address, data and control lines from
<>hardware on the frontpanel controller. You can access memory or I/O port
<>that way.
<In other words, make the front panel do a DMA access, either to memory or
<I/O port? That way it doesn't affect the CPU state at all, except the CP
<has to be running in order to handle the DMA grant.

Show me a simple mod that would make the Altair or IMSAI or their direct
decendants do it. I'd suggest looking at what they did do first as it
will limit your options.

As to what can be done with a clean sheet of paper I can give you the

        Good, Fast, Cheap: you may pick any two.


Received on Tue Feb 24 1998 - 20:58:16 GMT

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