[sebhc] Z-100 upgrade modules (ZMAX memory upgrade and ZCLK clock) available

Barry Watzman Watzman at neo.rr.com
Sat Apr 15 11:41:04 CDT 2006

The newer machines, of course, natively supported 768 megs of memory (3
banks of 256).  To change from 3 banks of 64 to 3 banks of 256 all you
needed to do was change a PAL or two.  The newer machines also supported an
8MHz 8088 instead of the 5MHz part that most machines shipped with.  There
was a formal upgrade kit from Heath that included all of the parts required
to do both modifications.  No cuts or jumpers were required, just chip
changes.  Which makes me question the point of ZMAX, since it only worked on
the later (2806) motherboards.

-----Original Message-----
From: sebhc-bounces at sebhc.org [mailto:sebhc-bounces at sebhc.org] On Behalf Of
Lee Hart
Sent: Saturday, April 15, 2006 12:30 PM
To: sebhc at sebhc.org
Subject: Re: [sebhc] Z-100 upgrade modules (ZMAX memory upgrade and ZCLK
clock) available

>> The 2nd item is a ZMAX - Z100 motherboard memory maximizer kit by Rick
>> Pegg and produced and marketed by Graymatter Applications Software.
>> Works only with later module Z-100 motherboards, does include written
>> instructions for the modifications, the 6 specialized chips required
>> and 27 (3 banks x 9 ICs per bank) 256K bit D-RAMS. Gives you a wacking
>> 768K bytes of memory!  You can also use the 32K RAM chips you remove
>> to upgrade the video system (instructions included).

Z-100's often came with 32k RAMs in the video board; they were really
64k RAMs that had a bad bit, and so were sold cheap. When you replaced
the 64k RAMs with 256k, you could move the old 64k RAMs to the video
board to get double the video memory. There were a few programs that
could use this extra memory.

Dan Lanciani wrote:
> Interesting; what are the 6 specialized chips?  We used to do this
> with one multiplexor (74LS157?) and a bent pin on the memory decode
> PAL.  Older machines needed a newer monitor ROM as well.

Technically, all you needed were the RAMs and the multiplexer. But it
took a lot of cuts and patches to do it that way. The various kits
provided the extra parts to make the upgrade easier.
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in    --    Leonard Cohen
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
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