Browse Prior Art Database

A Method for Address Parity Error Detection When Using External SRAMS for Directory Management

IP.com Disclosure Number: IPCOM000123162D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 69K

Publishing Venue

IBM

Related People

Benavides, A: AUTHOR [+3]

Abstract

This disclosure describes a method to detect addressing parity errors when updating and maintaining a coherency directory in external SRAMS.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 88% of the total text.

A Method for Address Parity Error Detection When Using External SRAMS
for Directory Management

   This disclosure describes a method to detect addressing
parity errors when updating and maintaining a coherency directory in
external SRAMS.

   Detecting addressing parity errors when updating and
maintaining a coherency directory in external SRAMs is important to
avoid system memory corruption.  The ECC of the entry to be written
includes the address and/or address parity information along with the
coherency information for the entry.  When an addressing error occurs
due to noise on a write to a coherency directory entry in the SRAMs,
a 'wild' memory location is updated.  The intended entry is
unaffected and still contains a good ECC but with stale coherency
information.  A read of the 'wild' directory information will detect
the parity error through the ECC error however it is unlikely that a
future coherency directory access will read the 'wild' directory
location before memory is corrupted due to the stale coherency data
in the directory.

   To avoid this problem, the data and ECC for a coherency
directory entry is distributed across multiple SRAMs and uses
multiple sets of address pins to drive the SRAMs.  When an
addressing error occurs due to noise on a write, it is unlikely that
all sets of address pins would get the same error since they use
different drivers and wiring paths.  Some of the SRAMs used to store
the directory entry would see the intended addres...