Z-80 hack

From: Allison J Parent <allisonp_at_world.std.com>
Date: Sat Aug 7 09:04:45 1999

<I've got a little job to do which would be easy with an AMPRO Little-Board
<like the REV-0 boards I have got, except that it's too slow. I was thinkin
<that the easiest way to do this thing is to take a Z-80H from the selected
<12MHz capable ones I have, team it up with a 64Kx8 SRAM, and a set of the

The number of mods to get a LB to run at 12mhz would be better invested in
building a new board from scratch.

<'A' type peripherals, provided I switch the clock to 4MHz each time I see a
<IORQ* or an (M1* & I/O*) or a RETI on the data bus during M1*, resetting th
<higher speed on the next M1*.

there is a wait line for this kind of stuff. I'd upgrade to faster
peripherals 6 or 8 mhz ones are still available.

The FDC, SIO, CTC, RAM(and timing chain) all have Tacc that are way to slow
for even 6mhz.

I hacked one to 8mhz and then put it back, it was never as solid in
operation.

<Have you ever tried something like that? What am I overlooking here?

Basic design. Many of the utilities are timing sensitive. Catch TCJ and
order some back issues for the 8mhz mod. The back issues are still
available.

Also get issue 79, the P112 board may really be what you want.

<I used to do things like that with the 65xx and 68xx parts all the time, bu
<never with a Z-80 because of the peripherals and the mode-2 interrupt, whic
<the AMPRO board probably doesn't even use.

The ampro does use mode 2, otherwise there is little point to using z80
peripherals.

allison
Received on Sat Aug 07 1999 - 09:04:45 BST