Rebirth of IMSAI

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Mon Mar 29 18:18:45 1999

At 01:06 AM 3/30/99 +0100, Tony wrote:

>
>> Actually, it might be as correct to say that 8088 signal names are more or
>> less like "all the other" microcomputers in the non-Motorola camp. with
the
>> 8085 and z-80, it became obvious that the large number of strange signals
>> generated by the 8080 didn't even help the Intel folks with the task of
>> interfacing the processor to memory and peripheral devices. The simple
>
>One of the problems with the S100 bus is that it is _very_ dependant on
>the 8080 signals. Even using a Z80 is a bit of work - things like PINTE
>(which indicates if interrupts are enabled) and SSTACK (address lines
>contain the value of the stack pointer) don't exist as external signals
>on the Z80.
>
Of course if you wire your own Z-80, you can ignore most of the weird
signals if you are using static ram. Just use a memory write signal for
writes, and another to gate read data onto the buss.

>Actually, I prefer the Motorola / PDP11 idea of having memory and I/O in
>the same address space. It means you can use the same instructions and
>addressing modes to access either.
>
There is nothing in the Z-80, etc. to prevent you from using memory mapped
I/O.
Of course if some peripheral hardware uses I/O instruction decoding, them
you use those instructions for its interface.
-Dave
Received on Mon Mar 29 1999 - 18:18:45 BST