Path: utzoo!utgpu!water!watmath!clyde!att!ucbvax!hplabs!well!ejf
From: ejf@well.UUCP (Erik James Freed)
Newsgroups: comp.sys.next
Subject: Re: NeXT Memory - No Error Checking or Parity !
Keywords: Memory,errors,parity
Message-ID: <7493@well.UUCP>
Date: 28 Oct 88 16:59:41 GMT
References: <549@gt-eedsp.UUCP>
Reply-To: ejf@well.UUCP (Erik James Freed)
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 26

In article <549@gt-eedsp.UUCP> jensen@gt-eedsp.UUCP (P. Allen Jensen) writes:
>Ok, Straight from a NeXT salesrep in response to the question:
>Q: Does the memory have a parity check bit ?
>A: "No"
>The reason was that "memory is reliable enough that the added cost
>was not justified."  If you have ever worked on some older equipment
>without parity, your opinion may differ.  Could an expert on RAM
>chips respond ?   Is memory really "reliable enough" ?
>I was supprised to learn that the cold-start diagnostics do not
>check memory for errors - they just look to see if there is any
>memory there.  If I had a NeXT, I think I would have a crontab
>entry to check memory every day/night !

I think it was Seymour Cray who was quoted as saying
	"Parity is for farmers"
I would tend to support NeXT's decision. Parity is supposed to allow
you to pinpoint where errors reside, but the software is rarely written
so that information is easily available. In general if your system memory
is flakey, you will soon realize that something is up and then you can
run memory tests to isolate the particular simm module. (I assume that a
good memory checking diagnostic will be available at a standalone level
for the NeXT) A useable (thorough) memory test takes a lot of time. It is 
not something that you want to run every boot up. And parity memory in
my experience just is not really that useful. (at least to justify the PC
real estate) I now submit myself to the flames
Erik