Browse Prior Art Database

Memory Card Select Net Failure Isolation

IP.com Disclosure Number: IPCOM000046500D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Schettl, MD: AUTHOR [+3]

Abstract

The symptoms of a failing storage card select net in a computer system vary depending on the exact failure (i.e., stuck active, stuck inactive, open interposer, open card, etc.). If several memory types are available on the system, the problem is compounded because the symptom of a failing card select net varies with the memory type. An extensive amount of diagnostic microcode is required to analyze all the symptoms to determine the failing net. The amount and complexity of the diagnostic microcode can be significantly reduced by adding a minimal amount of hardware.

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Memory Card Select Net Failure Isolation

The symptoms of a failing storage card select net in a computer system vary depending on the exact failure (i.e., stuck active, stuck inactive, open interposer, open card, etc.). If several memory types are available on the system, the problem is compounded because the symptom of a failing card select net varies with the memory type. An extensive amount of diagnostic microcode is required to analyze all the symptoms to determine the failing net. The amount and complexity of the diagnostic microcode can be significantly reduced by adding a minimal amount of hardware.

Consistency of failure symptoms regardless of the exact failure or memory card type is attained by sensing the storage card select net at the source. The card select nets are sampled during a memory access, and immediately following a memory access. In Fig. 1, card select driver 11 drives the memory card (not shown) and also drives card select receiver 12. The output of card select receiver 12 feeds exclusive OR circuit 13 which also has inputs from other card select receivers driven by other card select drivers in a manner similar to card select driver 11 and card select receiver 12. Exclusive OR circuit 13 has outputs at one and zero levels when an odd number of inputs are at a one level and an even number of inputs are at a one level, respectively.

The output of exclusive OR circuit 13 feeds latch 10 via inverter 14 and feeds latch 20 directly. Latches l0 an...