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From: eli@smectos.gang.umass.edu (Eli Brandt)
Newsgroups: comp.arch
Subject: Re: Workstation Data Integrity
Message-ID: <19208@dime.cs.umass.edu>
Date: 31 Aug 90 15:40:29 GMT
References: <6797.26d6edce@vax1.tcd.ie> <56qmo1w162w@zl2tnm.gp.govt.nz> <19875@crg5.UUCP>
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Reply-To: eli@smectos.CS.UMASS.EDU (Eli Brandt)
Organization: University of Massachusetts, Amherst
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In article <19875@crg5.UUCP> powell@crg5.UUCP (Powell Quiring) writes:
>In article <56qmo1w162w@zl2tnm.gp.govt.nz> don@zl2tnm.gp.govt.nz (Don Stokes) writes:
>>rwallace@vax1.tcd.ie writes:
>>
>>> If the operating system just told you about it when there was a parity error
>>> I'd agree with you, something like flashing up a message on the screen:
>>> "Parity error detected in code segment at 1234:5678, reboot? (Y/N) ".
>>> However automatically crasing the computer is NOT acceptable behaviour: I'd
>>> much rather do without the parity checking. Consider: suppose a parity error
>>> occurs on a 640K machine. The error is probably in either an unused area of
>>> memory (e.g. at the DOS prompt) or in a section of code that isn't going to b
>>> executed on this session with the program (e.g. error handling code).
>
>The fact that you got a parity error indicates that the memory has
>been read.  The only question is how much this incorrect value
>is going to screw you up.

How 'bout when you get a parity error a little window pops up with the mangled byte and some 
context?  That way you can fix it if it's in human-readable data and choose either to continue
or reboot otherwise.  I personally would always choose the latter - I don't want munged FP values,
I don't want corrupted FATs written to disk, and I really don't want a 21h call changed from 25h
to 35h.  Of course, you could always add a few error-correcting bits, too.  However, *I* wouldn't
pay for the extra RAM/circuitry/design time because I've never had a genuine parity error.