Browse Prior Art Database

Testing Microcode in a Paging Situation

IP.com Disclosure Number: IPCOM000079119D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Frye, HE: AUTHOR [+2]

Abstract

Paging can occur on a relocate machine when the microcode issues a write-main-store (WMS) microorder or a read (SDR). While the write or read operations are underway, it is necessary for the microcode to be capable of handling a paging interrupt at every possible memory reference. This description provides a technique of testing that capability by selectively injecting and analyzing paging faults. This is accomplished by: 1) adding a new function to the Diagnose instruction to force paging interrupts, and 2) providing software to utilize the modified Diagnose and do the analysis.

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Testing Microcode in a Paging Situation

Paging can occur on a relocate machine when the microcode issues a write-main-store (WMS) microorder or a read (SDR). While the write or read operations are underway, it is necessary for the microcode to be capable of handling a paging interrupt at every possible memory reference. This description provides a technique of testing that capability by selectively injecting and analyzing paging faults. This is accomplished by:
1) adding a new function to the Diagnose instruction to force

paging interrupts, and
2) providing software to utilize the modified Diagnose and do the

analysis.

The Diagnose instruction is modified in a manner similar to that described in IBM Technical Disclosure Bulletin, Volume 14, No. 1, June 1971, pages 231 and 232, "Diagnose and Multiply Retry Testing" by H. E. Frye, to provide a table of control words. The first control word causes a trap on counter overflow with no machine check. The second control word causes entry to a new microcode routine, which changes the Program Status Word (PSW) to DAT (Dynamic Address Translation) mode and attempts to read the address in the Storage Address Register (SAR) at the time of the trap. By providing test software with invalid hits in all entries, a paging interrupt is forced. The above figure is a flow chart of processing software to discard the interrupts at cycles where paging could not or should not occur.

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