From owner-freebsd-hackers Sun Oct 26 19:36:08 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id TAA09838 for hackers-outgoing; Sun, 26 Oct 1997 19:36:08 -0800 (PST) (envelope-from owner-freebsd-hackers) Received: from earth.mat.net (root@earth.mat.net [206.246.122.2]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id TAA09832 for ; Sun, 26 Oct 1997 19:36:03 -0800 (PST) (envelope-from chuckr@glue.umd.edu) Received: from picnic.mat.net (picnic.mat.net [206.246.122.117]) by earth.mat.net (8.8.7/8.6.12) with SMTP id WAA29481; Sun, 26 Oct 1997 22:35:34 -0500 (EST) Date: Sun, 26 Oct 1997 21:34:39 -0500 (EST) From: Chuck Robey X-Sender: chuckr@picnic.mat.net To: Alfred Perlstein cc: hackers@FreeBSD.ORG Subject: Re: Parity Ram In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk On Sun, 26 Oct 1997, Alfred Perlstein wrote: > > > Do you know anything of Richard Hamming's assertion that parity memory > > > (the old fashioned even/odd type) is-a-bad -thing in large > > > configurations? > > > > I think it bullshit. I've never heard of this before. Nor have you in > > the two times you've mentioned it, actually stated what is supposed to be > > so bad about it. > > more bits means more chance of error even if they are "error-correcting" > bits? Not unless the error rate is spectacularly high, Alfred. It's not that high (nearly within orders of magnitude) for RAM. The parity does some good, but ECC does better. The algorithms have existed for a long time, but the ability to do it inexpensively in hardware came a lot later. Parity is good, but ECC is far better, and with the current state of the hardware art, parity no longer competes. It used to. > > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@glue.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+-----------------------------------------------