Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!haven!udel!burdvax!barry
From: barry@PRC.Unisys.COM (Barry Traylor)
Newsgroups: comp.arch
Subject: Re: Parity in Internal Data Paths of Processors
Keywords: parity, error detection
Message-ID: <11398@burdvax.PRC.Unisys.COM>
Date: 8 Sep 89 04:53:44 GMT
References: <124311@sun.Eng.Sun.COM>
Followup-To: comp.arch
Organization: Unisys Corporation, Paoli Research Center; Paoli, PA
Lines: 15

In article <124311@sun.Eng.Sun.COM> kum@sccmts.Sun.COM (Kumar Venkatasubramaniam) writes:
> ...
>Are there large systems (mainframes, supercomputers) that 
>perform additional parity checks internally and under what
>conditions?  ...

The Unisys large A Series (A12/15/17) uses either parity or mod 3 residue
on not only data paths, but the results of alu operations.  Very few data
paths are not protected.  Residue is used wherever possible and practical.
In addition to the processor error checking, the processor will report a
"proc internal" error to software, which will attempt a single retry of the
instruction that discovered the error.

Barry Traylor
Unisys A Series Engineering