Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!bu.edu!inmet!arra
From: arra@inmet.inmet.com
Newsgroups: comp.sys.zenith
Subject: Memory Board Error, Seek Manual
Message-ID: <34600002@inmet>
Date: 12 Apr 91 18:36:00 GMT
Lines: 40
Nf-ID: #N:inmet:34600002:000:1600
Nf-From: inmet.inmet.com!arra    Apr 12 14:36:00 1991


I have a Z-248 with a memory card which has a problem, but I have no
documenation for it.

Memory Card:
	The card contains 128K conventional memory, rounding 512K up to 640K.
	This is with soldered 64K chips.
	It also has 1 Meg extended memory, base address at 1MB.
	This is with 512K soldered 256K chips, 512K socketed 256K chips.
	The card has the connectors for the extended Zenith slot.
	There are 3 2-pin jumpers labelled J403, J404, & J405.
	The writing on the chip side of the board says:
	85-3260-20 072286 Memory Board (then in big, 7-segment LCD-like
	characters, 0787)
	The back side of the board says: 050686 85-3260

The problem: the 128K contains a memory parity error, which occasionally
	occurs with software (presumably which accesses memory that high),
	and repeatedly occurs (at the same address) when I run the
	ROM-resident Zenith memory test. This test says to replace chip U407,
	which I did. However, the test still reports a memory parity error
	so I no longer trust the ROM test's chip identification.

The 1 Meg extended memory is OK. I would like to either
    1) fix the "parity" error on the 128K, or if I can't accomplish that,
    2) disable the 128K and still use the 1 MB extended memory.
I guess that the jumpers might be able to re-configure the board to accomplish
2), but without documentation, I'm lost.

Does anyone have any user documentation, or board schematic, for this board?

Thanks in advance,
=====================
 arra@inmet.inmet.com
 Arra Avakian
 Intermetrics, Inc.
 733 Concord Ave
 Cambridge, MA 02138
 (617)661-1840 x4500
=====================