Browse Prior Art Database

Compare Circuit Checking

IP.com Disclosure Number: IPCOM000086782D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Chan, SK: AUTHOR

Abstract

Described is a scheme of error checking for logical compare circuits. There are some areas in a data processing machine, as in the cache directory and the translation tables, where comparison of addresses are made to determine if the data resides in the cache or has been translated. The conventional way of error checking in such cases has been to parity check the two input busses. The data is then compared bit-per-bit, and the individual compares are AND'ed together to generate the overall compare. See Fig. 1.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Compare Circuit Checking

Described is a scheme of error checking for logical compare circuits. There are some areas in a data processing machine, as in the cache directory and the translation tables, where comparison of addresses are made to determine if the data resides in the cache or has been translated. The conventional way of error checking in such cases has been to parity check the two input busses.

The data is then compared bit-per-bit, and the individual compares are AND'ed together to generate the overall compare. See Fig. 1.

The drawing shows the method of doing a parity check after all the individual bits, including the parity bit, are compared.

Whereas the old scheme cannot detect errors in the bit-per-bit compare circuits, the logic will detect any single-error failure in either the bit-per-bit compare circuitry, or either one of its two input busses. Fig. 2 shows an example of the checking. The compare check is valid whether the two input busses compare or not. The scheme can be extended to any number of bits in the parity check field.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]