🚀 go-pugleaf

The early Z-158 CPU boards have been infamous in developing intermittant
parity problems.  All chips on these boards were socketed and there were so
many mods that there is a rats nest of wires on the back of them.  Most of these
parity failures defy locating because they are so erratic.  Sometimes reseating
the chips helps.  Best solution is to exchange the board with ZDS for the new
version.  The new version card is P/N 181-6792.  One old version is 181-5857
and I believe there is one other part number that is even older.  You can
exchange the card through a service center or through Heath parts for about
$200.00.

Hope this helps.

--
     Kent Phelps        | Internet:  kent@sun.ufnet.ufl.edu
 University of Florida  | UUCP:  ... ????
 Digital Design Facility| Phone: 904-335-8322

About getting "all" your 768K in a z-158
(and a possible memory board solution):

I added an expanded memory board to my z-158.  (As is often the case) the
board is capable of backfilling the main-memory space before starting the
EMS.  So I took the third bank of 256K chips off my memory board and added
them to the EMS board, then let it backfill from 512K up to 640K.  It added
the "unused" 128K to its total EMS.  So in effect the EMS board gave me
an eighth-Meg more memory than I bought for it...

As for the "rats' nest of wires" memory board problem, I discovered in
the course of playing around that I could take _all_ the chips off my
memory board and put them on the EMS board --- it successfully
backfilled the entire 640K.  I don't do this because it seems kind of
suspect to me, and my memory board is okay (actually, I seem to have a
chip failure in one of my EMS chips, but I can't diagnose that!  argh).
But it might get you out of a problem without having to spring for a
replacement mem. board.

And a final neat feature:  Chris Dunford/Cove Software distributes a free
program called EEMRAM that can map Enhanced expanded memory into the address
space between 640K and a CGA adaptor.  No hardware mods needed, and my
machine reports 736K of main memory.  I love it!

My board:
	RAMPARTNER 2-Meg EEMS/EMS board
	PC Technologies, Inc.
	Ann Arbor, MI  48108
	313/996-9690

What I got is LIM 3.2/EEMS compatible, they may be compatible with LIM
4.0 by now.  Or they might be out of business; I haven't been following
along to know.

bob,mon.

     Kent Phelps  [Internet:  kent@sun.ufnet.ufl.edu] writes:
The early Z-158 CPU boards have been infamous in developing intermittant
parity problems.
............................

	Damn.  3 of 12 Z-158s I have (about 2 1/2 yrs. old) have
started to show intermittant parity errors in the past several months.
I thought we must be doing something wierd.  This makes it sound as if
we should just consider it a lost cause and junk the memory boards
when the problem gets annoying.  Is that true or is there another
reasonable course?

When I got that error, I found that shutting off the computer for a
while (5 minutes... really drain those caps) would solve the problem.
In fact, I thought the problem was that I had been power cycling too
quickly.

Our repair department says that a ROM replacement fixes the problem on
the Z157.

Hope some of that info was helpful,
Tom
-- 
Tom Limoncelli       The computer industry should spend more time in front of
tlimonce@drew.uucp              their computers.  Remember when "Look & Feel"
tlimonce@drew.Bitnet                      was what you tried to do on a date?
limonce@pilot.njin.net