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Realtime Field Replaceable Unit Isolation for Parity Errors

IP.com Disclosure Number: IPCOM000109599D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Price, WE: AUTHOR [+3]

Abstract

This article describes a circuit arrangement which solves the problem of field replaceable unit (FRU) isolation of RAM in processing systems based on the Intel 80486 when intermittent or soft parity errors are experienced. (Image Omitted)

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 63% of the total text.

Realtime Field Replaceable Unit Isolation for Parity Errors

       This article describes a circuit arrangement which solves
the problem of field replaceable unit (FRU) isolation of RAM in
processing systems based on the Intel 80486 when intermittent or soft
parity errors are experienced.

                            (Image Omitted)

      In systems using the 80486 microprocessor, the microprocessor
has the responsibility of parity error checking.  The 80486 processor
checks for parity errors and indicates the parity status using a
Parity Check Output (PCO) signal.  Driving the PCO is the only effect
that bad parity has on the 80486 processor.  For systems using parity
error checking, the system must vector the interrupt (INT) back to
the processor.  Unfortunately, the PCO signal is not available to the
system until one cycle after the read is completed.  In addition, a
cycle is required to generate an interrupt to inform the processor of
the parity error and force it into an error routine.  Since at least
two cycles have been executed since the read cycle was completed and
the instruction being executed is not responsible for the error, it
becomes difficult to determine the source of the parity error.
Difficulty is increased with the addition of bus masters.

      The circuit arrangement disclosed herein is shown in functional
block diagram in the drawing.  The problem can be solved by capturing
the row address select (RAS) s...