From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263693AbTDTUbm (ORCPT ); Sun, 20 Apr 2003 16:31:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263696AbTDTUbm (ORCPT ); Sun, 20 Apr 2003 16:31:42 -0400 Received: from fluent2.pyramid.net ([206.100.220.213]:55968 "EHLO fluent2.pyramid.net") by vger.kernel.org with ESMTP id S263693AbTDTUbl (ORCPT ); Sun, 20 Apr 2003 16:31:41 -0400 X-Not-Legal-Opinion: IANAL I am not a lawyer X-For-Entertainment-Purposes-Only: True Message-Id: <5.2.0.9.0.20030420132915.01d28c40@fluent2.pyramid.net> X-Mailer: QUALCOMM Windows Eudora Version 5.2.0.9 Date: Sun, 20 Apr 2003 13:43:40 -0700 To: linux-kernel@vger.kernel.org From: Stephen Satchell Subject: (OT) md5sum proving to be an EXCELLENT memory test In-Reply-To: References: <6uwuhpl2u5.fsf@zork.zork.net> <6uwuhpl2u5.fsf@zork.zork.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Because the subject of "bad RAM" comes up from time to time on this list, I thought I would post an observation I made over the weekend. I was working with some server boxes with "generic" RAM that would mis-behave from time to time, and I really didn't understand why that would happen. The misbehavior included some OOPSes from time to time, but they would be random and so I didn't report them. Then I started to grab Red Hat Linux version 9, and because the server boxes were the only ones with enough open disk space I started to download the ISO images to them. Imagine my surprise when I went to run md5sum to check the download -- they would fail the test. Perform the test multiple times, and the failure pattern would CHANGE. (Copy the ISOs to another system via sftp, along with the MD5SUM, and they checked as perfect.) Perform md5sum on the files on the server and save the results, and the signatures would be different from run to run on the same files. Incompatible RAM. Proof: do a kernel computer, get signal 11. Put the "right" RAM in the boxes (in this case, a Viking PE8641U4SN3L-CL3 64-MB stick in an Intel CA810E motherboard) and both md5sum and a kernel compile worked just swell. By the way, md5sum on small files worked perfectly on these server boxes with IFA (Taiwan) 128-MB RAM installed, but on large files it would create the varied signatures. So, along with the test of compiling a kernel and seeing if you get signal 11 messages, you can also load up some large files and run md5sum on them a couple of times. With six ISO images totalling 1.4 GB, it took a 500-MHz Pentium II about five minutes to run through the files and show the errors -- an order of magnitude faster than trying to do a kernel compile. FWIW Stephen Satchell