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Detecting Storage Address Failures with Data Parity

IP.com Disclosure Number: IPCOM000091068D
Original Publication Date: 1969-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Freiman, CV: AUTHOR [+3]

Abstract

The same parity bits used to detect data errors in computer systems can also be used to detect addressing errors within the system storage unit, if parts of a data word are stored in different sections of the storage unit. This is accomplished by physically separating the parity bits from the data they are covering at the storage level.

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Detecting Storage Address Failures with Data Parity

The same parity bits used to detect data errors in computer systems can also be used to detect addressing errors within the system storage unit, if parts of a data word are stored in different sections of the storage unit. This is accomplished by physically separating the parity bits from the data they are covering at the storage level.

It is assumed that a data word is made up of six bytes, two bytes of each word being stored in each of three basic storage modules BSM. During data transfer to the storage unit, the usual byte parity is generated, PO for byte 0, P1 for byte 1, etc., to 25 for byte 5. When storing the word in the BSM's, the parity bits for the two bytes of data contained in each BSM are distributed over the other BSM's as shown. For example, P0 can be stored as the parity bit for byte 3 in BSM 2, P1 can be stored as the parity bit for byte 4 in BSM 3, and so on, as shown. This can be done by crossing cable wires in the storage area.

When reading the word back from storage, the parity bits are realigned with their bytes and the usual parity read check is made. If one of the BSM's accesses an incorrect address, the parity bits within that BSM do not correctly associate with their original data bytes and a parity error is indicated. Thus, a parity error indication when reading back indicates that there is either a data error or a storage address error. Whether the error involved is in the data or in...