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From: davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr)
Newsgroups: comp.arch
Subject: Re: Workstation Data Integrity
Message-ID: <2496@crdos1.crd.ge.COM>
Date: 6 Sep 90 19:40:09 GMT
References: <6797.26d6edce@vax1.tcd.ie> <56qmo1w162w@zl2tnm.gp.govt.nz> <19875@crg5.UUCP> <19208@dime.cs.umass.edu> <1990Sep6.141040.3244@mozart.amd.com>
Reply-To: davidsen@crdos1.crd.ge.com (bill davidsen)
Organization: GE Corp R&D Center, Schenectady NY
Lines: 13

In article <1990Sep6.141040.3244@mozart.amd.com> davec@nucleus.amd.com (Dave Christie) writes:

| Its been many years since I designed EDAC for a 64-bit machine, but what
| I seem to remember is that using 7 bits would only allow you to correct
| the 64-bit data portion, not the 7 check bits themselves.  To cover those
| you need one more bit (and you really do want those covered as well). 

  I just looked at some C code for Hamming code I wrote years ago, and
it appears to need log2(N)+1 bits, including the EDAC bits themselves.
In any case, if you can have EDAC for the price of parity, why not?
-- 
bill davidsen	(davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen)
    VMS is a text-only adventure game. If you win you can use unix.