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From: unknown@ucscb.UCSC.EDU (The Unknown User)
Newsgroups: comp.sys.apple2
Subject: Re: speed loss
Message-ID: <14708@darkstar.ucsc.edu>
Date: 19 Apr 91 08:26:28 GMT
References: <9104181535.AA28525@apple.com>
Sender: usenet@darkstar.ucsc.edu
Organization: University of California, Santa Cruz; Open Access Computing
Lines: 20


In article <9104181535.AA28525@apple.com> THROOP@GRIN1.BITNET ("Throop,Henry B") writes:
>[toddpw writes about RAM refreshing]
>
>Does this have anything to do with why IBM systems use 9 RAM chips (for
>parity checking?) where 8 do in the gs?

	No.. The hardware parity checking seems to me like a hell of
a big waste of dinero/moolah/cash/money...

	It has nothing to do with RAM refreshing.. As you said, it's parity
checking.. 
	I don't know whether they work on odd or even parity, but the
extra bit is set so that there are an odd (or even) number of ones 
in the whole 9 bits.. The parity bit will show if there is ONE bit 
error in the byte, but I believe it tells absolutely nothing about where
the error is, like some other checks..	
-- 
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