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             ISA Bus: Symptoms/Solutions: Parity Error Problems            
                                                                           
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PARITY CHECK 2 ERROR IN DESKPRO 286 12 MHZ

  If you get this message after installing an Above Board or Matched Memory
  Classic, it is likely you have overlapping conventional memory, (both the
  Above Board or Matched Memory Classic, and the Compaq motherboard are
  trying to supply conventional memory).

  There are two ways to correct this problem:

  1.   The first is to temporarily disable the Compaq motherboard memory
       down to 256K or 512K. (If the error is Parity Check 2 40000,
       disable motherboard memory down to 256K, if the error is Parity
       Check 2 80000, then disable motherboard memory down to 512K).
       There are three steps to this procedure:

       a.   The Compaq motherboard switch block is located on the front
            left corner of motherboard.

       SWITCHES   2      3     MEMORY SIZE
                 ON     ON     Disable RAM and ROM
                 ON     OFF    Limit motherboard to 256K
                 OFF    ON     Limit motherboard to 512K
                 OFF    OFF    Enable all base memory, 640K max

       b.   Rerun SETBOARD.  Tell the Above Board or Matched Memory
            Classic to supply NO conventional memory.
       c.   Set Compaq motherboard switches back to 640K.

  2.   The second method of eliminating this problem is to find a way to
       rerun SETBOARD without first correcting the conventional memory
       overlap. There are four steps to this approach:

       a.   Temporarily remove the Above Board or Matched Memory Classic
            from the system.
       b.   Copy the SETBOARD.EXE program from the Above Board / Matched
            Memory Classic installation diskette to the hard disk.
       c.   Reinstall the board.
       d.   Rerun SETBOARD from the hard disk and set the Above Board or
            Matched Memory Classic to supply NO conventional memory.

  NOTE:     Overlapping conventional memory causes Parity Check 2 errors
            during floppy disk accesses.  If the Above Board or Matched
            Memory Classic is removed while SETBOARD is being copied to
            the hard disk, there will not be a Parity Check 2 error. When
            the Board is reinstalled and SETBOARD is run from the hard
            disk, SETBOARD should be able to successfully reprogram our
            board without a parity error occurring.  People who do not
            feel comfortable changing motherboard switches should use
            this approach.

PARITY CHECK 1

  A Parity Check 1 error indicates a memory problem on the computer's
  mother/system board.  Sometimes moving the Above Board to a different slot
  helps.  HOWEVER ....

  If system is an IBM PC/AT and user is using Above Board software diskette
  version 4.0 WITHOUT A REVISION NUMBER and getting "PARITY CHECK 1 10000
  (S)", the problem is with EMM 4.0.  The error is often intermittent and
  occurs just as the EMM page count is finishing. Version 4.0 Rev A (or
  newer) will correct this problem. The latest software is available on
  Intel's BBS.

PARITY CHECK 2

  Generally this indicates a failure of memory chips on any add-in board or
  a memory conflict.

  Steps to follow in troubleshooting:

  Check the number that follows the Parity Check 2 message.  Most often it
  will be 40000, 80000, or sometimes 90000. A 40000 address usually
  indicates overlapping memory at the 256K address (they computer is
  supplying memory from 256K to 512K or 640K, and the Above Board was set to
  provide the same thing). An 80000 or 90000 indicates overlapping memory
  between 512K & 640K.

  The only solution to this problem is to rerun the SETBOARD program.  If
  the error is fatal (system won't boot), then they must move the board to a
  system with less than 512K on the motherboard to run SETBOARD. If the
  error occurs when accessing the floppy diskette, it will be necessary to
  pull the Above Board, copy SETBOARD.EXE to the hard disk, put the Above
  Board back into the computer, and run SETBOARD from the hard disk. (Intel
  DOES NOT ship boards supplying conventional memory!)

  For all other occurrences of Parity Check 2:

  1.   Check system bus speed.  If system runs at >8MHz, then be sure
       SETBOARD has been run to set up for correct bus speed.
  2.   Try running SETBOARD, setting up for 10MHz w-150ns chips.  This
       adds the maximum number of wait states to the Above Board.
  3.   Run the Intel TESTAB diagnostics program.
  4.   Check brand of memory chips (See Compatibility - Memory Chips.)
       Don't assume this is the problem until you have exhausted all
       other possibilities.
  5.   If system has a 10MHz bus & SETBOARD has ALREADY been run and set
       for the faster bus speed, then try re-running SETBOARD & setting
       for 8Mhz bus. Some 10MHz clones need the Above Board to be set for
       8MHz.
  6.   If the Above Board is providing expanded memory, there might be a
       reserved memory conflict, check the Reserved Memory Conflict
       section for more details.

REUSED MEMORY CHIPS

  Some users desolder memory chips from other boards and reuse them in Above
  Boards or sell them to others who use them in Above Boards.  The
  desoldering process can leave resin on the chips, and the resin can cause
  intermittent memory problems.



End of file                 Intel FaxBack # 1162          December 2,1992
