From owner-freebsd-hackers Wed Oct 29 12:12:41 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id MAA10302 for hackers-outgoing; Wed, 29 Oct 1997 12:12:41 -0800 (PST) (envelope-from owner-freebsd-hackers) Received: from smtp04.primenet.com (smtp04.primenet.com [206.165.5.85]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id MAA10295 for ; Wed, 29 Oct 1997 12:12:37 -0800 (PST) (envelope-from tlambert@usr07.primenet.com) Received: (from daemon@localhost) by smtp04.primenet.com (8.8.7/8.8.7) id NAA14399; Wed, 29 Oct 1997 13:12:36 -0700 (MST) Received: from usr07.primenet.com(206.165.6.207) via SMTP by smtp04.primenet.com, id smtpd014388; Wed Oct 29 13:12:33 1997 Received: (from tlambert@localhost) by usr07.primenet.com (8.8.5/8.8.5) id NAA18109; Wed, 29 Oct 1997 13:12:30 -0700 (MST) From: Terry Lambert Message-Id: <199710292012.NAA18109@usr07.primenet.com> Subject: Re: Parity Ram To: karpen@ocean.campus.luth.se (Mikael Karpberg) Date: Wed, 29 Oct 1997 20:12:30 +0000 (GMT) Cc: dg@root.com, hackers@FreeBSD.ORG In-Reply-To: <199710290229.DAA07708@ocean.campus.luth.se> from "Mikael Karpberg" at Oct 29, 97 03:29:12 am X-Mailer: ELM [version 2.4 PL23] Content-Type: text Sender: owner-freebsd-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > > 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, or something, > possibly clocked at multiple of the bus clockspeed, and therefor > not effect the rate at which memory could be read/written over the bus > by the CPU. I'd personally think using a static column dram would do the trick... Also, there's no real reson the write can't return and leave the cell calculating the ECC on it's on. It would make rereferencing the area take a wait, possibly, if the rereference was immediate. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.