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From: mark@mips.UUCP
Newsgroups: comp.arch
Subject: Re: Double-bit errors and ECC memory
Message-ID: <686@obiwan.UUCP>
Date: Wed, 16-Sep-87 13:23:30 EDT
Article-I.D.: obiwan.686
Posted: Wed Sep 16 13:23:30 1987
Date-Received: Sat, 19-Sep-87 08:49:34 EDT
Lines: 38

In article <8587@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes

	> Clearly, what we need, urgently, is ECC on the damn memory
	> chips.  There have already been mutterings about this, but no
	> commercial products as far as I know.

Micron Technology's 256Kbit dynamic RAM has on-chip ECC.  And customers
just frigging HATE the idea.  You shoulda been there (NY Hilton, Feb 1985)
at ISSCC when Jim O'Toole of Micron Technology faced an angry mob of
non-believers and tried to explain the advantages of on-chip ECC.  Poor
guy got hooted off the platform.

The gripes against ECC are (1) it's "dishonest" because it lets mfrs
sell defective chips.  {This was also heard three years previously
when redundant memories were first discussed.}  (2) There's no way to
tell whether a given chip has a hard error {ECC masks it}, in which
case the single-bit ECC provides no protection against soft errors.
Note that a hard error can occur weeks after system installation
so special RAM chip "test modes" aren't useful here.

Big customers (the ones that DRAM mfrs seek to please!) have a
Component Qualification and Reliability group, who qualify and/or
disqualify RAM vendors.  If the head of this group doesn't want
ECC RAMs, then he doesn't qual them and that company doesn't buy
them.  Sadly, the most savage attacks on Mr. O'Toole of Micron
came from the heads of Qual depts. of immense DRAM consumers.
Most notable among them was Mr. X of Burroughs (Unisys) who also
led the battle against redundant RAMs three years before.

DRAM mfrs therefore *perceived* that ECC RAMs were poison in the
(major customer) marketplace, so they backed away from the idea
PRONTO.  In fact, I believe (don't know for sure) that even Micron
Technology gave up on ECC and left it off their 1-Megabit DRAM.
You can call them in Boise, Idaho to find out.
-- 
-Mark Johnson	*** DISCLAIMER: The opinions above are personal. ***	
UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!mark   TEL: 408-720-1700 x208
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