Digital Equipment Corporation

Norbert H Riegelhaupt

Thomas D Bissett

William F Bruckert

Mitch Berkson

A memory for storing data in a computer system. Integrity of data transferred to or from a memory array is monitored by transferring two sets of EDC or ECC data corresponding to a longword of data between the memory array and two separate memory controllers. The probability of an undetected error is very low because the two sets of EDC or ECC data are compared to ensure that they match. The number of lines and pins used is minimized by multiplexing the EDC or ECC data with address signals and cycle type signals. The address and cycle type signals are placed on the time division multiplexed bidirectional lines at the beginning of a memory transfer cycle, and the EDC or ECC data is placed on these time division multiplexed lines at times when a longword of data is being transferred on a set of bidirectional data lines.

Memory device with transfer of ECC signals on time division multiplexed

A dual processor computer system with error checking includes a first processing system for executing a series of instructions including output instructions. A second processing system executes the series of instructions independently of and in synchronism with the first processing system. Shared resource devices are coupled to the first and second processing systems for receiving data from output instructions from the first and second processing systems substantially simultaneously. Error checking devices are located downstream of the shared resource means for checking the data received from the first and second processing systems only following a write operation into the shared resource means.

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Framingham, MA, United States of America

Norbert H Riegelhaupt