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From: manson@utecfc.UUCP (Bob Manson)
Newsgroups: net.micro.pc
Subject: Re: IBM-PC MEMORY PROBLEM
Message-ID: <63@utecfc.UUCP>
Date: Wed, 19-Feb-86 17:23:52 EST
Article-I.D.: utecfc.63
Posted: Wed Feb 19 17:23:52 1986
Date-Received: Wed, 19-Feb-86 20:45:20 EST
References: <1113@ihlpa.UUCP>
Reply-To: manson@utecfc.UUCP (Bob Manson)
Distribution: net
Organization: Engineering Computing Facility, University of Toronto
Lines: 61
Summary: 

Several months ago, someone asked what a PARITY CHECK 2 error was.  I
replied directly, but I don't know if the information was ever received
(I may not have included a return address).  Since someone else has a 
memory problem, I thought that I would simply post my answer. 

An item in the User-to User column in the 30 October 1984 issue of PC
Magazine gave a description of what a parity check error is and how to
identify the chips associated with the error.  Basically, a PARITY
CHECK 1 error means that you have a problem with the memory on the
mother board.  PARITY CHECK 2 would indicate a problem with the memory
on an expansion card.


Along with the PARITY CHECK error message, apparently an address code
is also displayed.  According to the man who wrote the letter(Wesley K.
Merchant), if you can't read the address code, (the error message will,
in the case of failure during diagnostics, scroll past fairly rapidly)
you should obtain a copy of the IBM advanced diagnostics, enable the
error logging and loop on the memory test.  (Diagnostic programs are
sometimes included when you buy expansion boards).  When the memory
failure occurs, the address code--in the form XYZZ 201, where 201 would
indicate a memory error--can be deciphered using the following table:


The "X" portion of the address identivies which 64K bank is
failing.

0YZZ = 1ST 64K BANK (0-64K)	5YZZ =  6TH 64K BANK (320-384K)
1YZZ = 2ND 64K BANK (64-128K) 	6YZZ =  7TH 64K BANK (384-448K)
2YZZ = 3RD 64K BANK (128-192K)	7YZZ =  8TH 64K BANK (448-512K)
3YZZ = 4TH 64K BANK (192-256K) 	8YZZ =  9TH 64K BANK (512-576K)
4YZZ = 5TH 64K BANK (256-320K)	9YZZ = 10TH 64K BANK (576-640K)

The "Y" portion of the address is NOT important unless you have
the old 16K chips. It will identify the failing 16K bank.


X0ZZ = 1ST 16K ROW 		X8ZZ = 3RD 16K ROW
X4ZZ = 2ND 16K ROW		XCZZ = 4TH 16K ROW


The "ZZ" portion of the error message is the BINARY number of the
64K chip in the indicated 64K bank

XY00 = PARITY CHIP		XY10 = DATA BIT 4
XY01 = DATA BIT 0 		XY20 = DATA BIT 5
XY02 = DATA BIT	1		XY40 = DATA BIT 6
XY04 = DATA BIT	2       	XY80 = DATA BIT 7
XY08 = DATA BIT	3		XYAA = EMPTY BANK-CHECK SWITCHES 
				XYFF = EMPTY BANK-CHECK SWITCHES 


I hope this helps.


-----------------------------------------------------------------
Bob Manson
University of Toronto
Department of Civil Engineering
Toronto, Ontario