ZX81 and 6116

From: Richard Erlacher <edick_at_idcomm.com>
Date: Mon Mar 25 01:06:37 2002

Has anybody ever tried sticking a 61512 extracted from the cache array on an
old '486 board onto a daughterboard with the CPU in one of these boxes?

I've done that with quite a number of different Z80's and had pretty good
luck. What makes it work really well, but limits the application to those
cases in which the memory map is monolithic, is modifying the system ROM to
include a routine to copy the ROM into the SRAM on hard reset, and then
disabling itself by means of a flipflop that is set when the top address is

I can provide details, but, believe me, it has saved me lots of hassle with
memory interfaces, since DRAMs often go wierd and require considerable effort
to fix, since they're often stupidly designed. SRAMs as you are trying to
replace are generally less likely to go bonkers, but if you want to expand the
memory, the method I've suggested works rather well and maxes out the memory
map. It also allows you to increase the CPU speed considerably.

----- Original Message -----
From: "Pete Turnbull" <pete_at_dunnington.u-net.com>
To: <classiccmp_at_classiccmp.org>
Sent: Sunday, March 24, 2002 7:15 PM
Subject: Re: ZX81 and 6116

> On Mar 23, 12:58, Dave McGuire wrote:
> > On March 23, Pete Turnbull wrote:
> > > Zilog made a "quasi-static RAM" 4K x 8, called Z8132, but it's
> > > 28-pin.
> >
> > I think that's the Z6132...interesting chip...
> Oops, typo. Yes, it's a 6132. I still have a few.
> --
> Pete Peter Turnbull
> Network Manager
> University of York
Received on Mon Mar 25 2002 - 01:06:37 GMT

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