Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!baum
From: baum@Apple.COM (Allen J. Baum)
Newsgroups: comp.sys.next
Subject: Re: NeXT Memory - No Error Checking or Parity !
Message-ID: <22342@apple.Apple.COM>
Date: 17 Dec 88 00:00:19 GMT
References: <549@gt-eedsp.UUCP> <8348@alice.UUCP> <1429@cpoint.UUCP> <854@calvin.EE.CORNELL.EDU>
Reply-To: baum@apple.UUCP (Allen Baum)
Organization: Apple Computer, Inc.
Lines: 14

[]
>In article <1429@cpoint.UUCP> alien@cpoint.UUCP (Alien Wells) writes:
>>As you can see, by the time you get to 64 bit memory - there really isn't a
>>reasonable excuse to not use EDC.

Um, theres a slight gotcha in doing ECC on a 64 bit chunk. Its not possible
to write a byte anymore. You must read all 64 bits, substitute the byte,
and write the 64 bits+new ECC. This is generally a sufficient reason to 
avoid ECC in low cost systems. Note that if you have a cache that reads and
writes 64 bit chunks to main memory anyway, it may not be a big deal, until
you have to worry about handling uncached writes, memory mapped i/o, ......
--
		  baum@apple.com		(408)974-3385
{decwrl,hplabs}!amdahl!apple!baum