Tandem Computers Incorporated

Hewlett-Packard Development Company, L.p.

Compaq Computer Corporation, Inc.

Russell Mark Rector

Mizanur Mohammed Rahman

Peter L Fu

Fred C Sabernick

Martin J Grosz

Jeff A Sprouse

Robert L Jardine

Jeff Sprouse

In an implementation of time of day response, time logic executed by each processor element of a logical processor generates a logical time in response to a time of day request. The logical time is generated to approximate the actual time such that each processor element of the logical processor returns the same logical time.

Time of day response

A processor interface chip and a maintenance diagnostic chip are provided coupled with two microprocessors designed to be run in tandem. The processor interface chip includes logic for interfacing between the microprocessors and a main memory, logic for pipelining multiple microprocessor requests between the microprocessors and main memory, logic for prefetching data before a microprocessor issues a read request, logic for allowing a boot to occur from code anywhere in physical memory without regard to the microprocessors' fixed memory location for boot code, and logic for intelligently limiting the flow of interrupt information over a processor bus between the microprocessors and the processor interface chip. The maintenance diagnostic chip includes logic to halt either of the microprocessors if an error is detected, and read out the state of the microprocessors and a secondary cache attached to the microprocessors, before the state of the microprocessors at the time of the fault changes to a different state which might hide evidence of the cause of the fault.

Processor interface chip for dual-microprocessor processor system

Microprocessor interface apparatus having a boot address relocator, a

Method of state determination in lock-stepped processors

Growing community of inventors

Oakland, CA, United States of America

Russell Mark Rector