From owner-freebsd-hackers Tue Oct 28 19:53:06 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id TAA16277 for hackers-outgoing; Tue, 28 Oct 1997 19:53:06 -0800 (PST) (envelope-from owner-freebsd-hackers) Received: from out2.ibm.net (out2.ibm.net [165.87.194.229]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id TAA16241 for ; Tue, 28 Oct 1997 19:52:45 -0800 (PST) (envelope-from mouth@ibm.net) Received: from slip129-37-195-113.nc.us.ibm.net (slip129-37-195-113.nc.us.ibm.net [129.37.195.113]) by out2.ibm.net (8.8.5/8.6.9) with SMTP id DAA160472 for ; Wed, 29 Oct 1997 03:52:38 GMT From: mouth@ibm.net (John Kelly) To: hackers@FreeBSD.ORG Subject: Re: Parity Ram Date: Wed, 29 Oct 1997 04:53:53 GMT Message-ID: <345abf0a.135742743@smtp-gw01.ny.us.ibm.net> References: <199710290229.DAA07708@ocean.campus.luth.se> In-Reply-To: <199710290229.DAA07708@ocean.campus.luth.se> X-Mailer: Forte Agent 1.01/16.397 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by hub.freebsd.org id TAA16271 Sender: owner-freebsd-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk On Wed, 29 Oct 1997 03:29:12 +0100 (CET), Mikael Karpberg wrote: >> In order to update the memory, the ECC must be recalculated over the >> entire 64bit quadword. This escentially means that you have to read the >> memory first, apply the changes/calculate the new ECC and then write it >> back. Obviously,this makes memory writes quite a bit slower. > >Hmm... It's still not quite clear to me. That is, does this slow my >computer down, in case I use ECC? > >It seems to me all this could be done on the DIMM/SIMM I believe IBM, HP, and other servers which require x40 SIMMS perform ECC without any slowdown due to calculation overhead in the memory controller, as is true of the Intel approach to ECC with x36 SIMMS and the 430HX chipset and cousins. Of course those would be high end machines not affordable for many users. John