Browse Prior Art Database

Bit Substitution Memory System

IP.com Disclosure Number: IPCOM000095484D
Original Publication Date: 1964-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hallock, DG: AUTHOR

Abstract

Addition of an auxiliary bit plane and bit substitution logic to a memory system allows the memory to tolerate one unswitchable bit storage element per word without loss of memory cycles. Such is by detecting the unswitchable bit and substituting the auxiliary bit.

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Bit Substitution Memory System

Addition of an auxiliary bit plane and bit substitution logic to a memory system allows the memory to tolerate one unswitchable bit storage element per word without loss of memory cycles. Such is by detecting the unswitchable bit and substituting the auxiliary bit.

Certain types of memory are subject to the presence of inoperative bit storage elements. These produce no detectable signal for either 1 or 0, while operative bit storage elements produce 1 signals of a first polarity and 0 signals of the opposite polarity. Thus, an operative bit storage element always produces one signal or the other. An inoperative bit storage element produces a null. This effect allows the detection of the inoperative bit storage element and substitution of the auxiliary bit storage element.

The memory readout is to a memory data register, having two flip-flops and logic for each position, and to a substitute bit position. Each position includes MDR flip-flop 1, auxiliary flip-flop 2 and Or 3. Flip-flop 2 is settable by either a 1 or 0 signal. Lack of either signal leaves flip-flop 2 unset. The reading mechanism for each bit also includes sense amplifiers 4, And's 5... 7 and Or's 8 and 9. Bit 1 position is fully illustrated. Other bit positions, including the partially illustrated Bit N position, are similar.

The substitute bit position includes substitution flip-flop 11, input Or's 12 and 13, sense amplifier 14, and And 15. The auxiliary bit plane is...