Browse Prior Art Database

Fault-Tolerant Memory Array Design

IP.com Disclosure Number: IPCOM000105331D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Broccoli, S: AUTHOR [+4]

Abstract

An error correction coding scheme together with a scheme of assigning bit positions of encoded words for fault-tolerance of memory array failures are disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 77% of the total text.

Fault-Tolerant Memory Array Design

      An error correction coding scheme together with a scheme of
assigning bit positions of encoded words for fault-tolerance of
memory array failures are disclosed.

      In a memory array chip composed of 8 word-line modules (WLM),
each of which contains 4Kx9 bits, 8 sets of 9 bits are fetched or
stored in every storage access.  Three such array chips are used to
access 8 sets of 27 bits in parallel.  A (27,19) ECC (error
correcting code) is used to provide fault-tolerance of WLM failures.
All errors generated from a WLM failure are correctable and all
errors generated from two WLM failures are detectable.

      The (27,19) ECC has 8 check bits for every group of 19 data
bits.  The parity check matrix of the ECC is shown in Fig. 1.  The
matrix is divided into 3 submatrices whose column positions
correspond to the bit positions stored in 3 array chips, which are
labeled as C1, C2, and C3.  Each ECC word is divided into 3
sub-words, each of which is stored in a separate chip.

      In a given storage access, 8 sets of 27-bit ECC words are
fetched or stored.  These 8 ECC words are labeled as A,B,C,D,E,F,G,
and H.  Fig.  2 shows the assignment of the first 9 bits of each ECC
word in chip C1.  Note that bits 2 and 3 of each ECC word are stored
in the same WLM, and bits 1, 4-9 of each ECC word are stored in more
than one WLM.

      The set of correctable errors includes all 27 single bit errors
and three doubl...