From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 28 Jul 2001 20:38:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 28 Jul 2001 20:37:56 -0400 Received: from hawk.mail.pas.earthlink.net ([207.217.120.22]:46471 "EHLO hawk.mail.pas.earthlink.net") by vger.kernel.org with ESMTP id ; Sat, 28 Jul 2001 20:37:43 -0400 Message-ID: <047c01c117c6$a86d1890$1125a8c0@wednesday> From: "J. Dow" To: "Kurt Garloff" , "David Lang" Cc: "Alan Cox" , , , , "Arjan van de Ven" , "Chris Brady" In-Reply-To:

<20010728131159.B23174@pckurt.casa-etp.nl> Subject: Re: VIA KT133A / athlon / MMX Date: Sat, 28 Jul 2001 17:37:32 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Original-Recipient: rfc822;linux-kernel-outgoing From: "Kurt Garloff" On Fri, Jul 27, 2001 at 05:23:07PM -0700, David Lang wrote: > I have a 1u box at my des that has two MSI boards in it with 1.2G athlons. > at the moment they are both running 2.4.5 (athlon optimized), one box has > no problems at all while the other dies (no video, no keyboard, etc) > within an hour of being booted. Somebody told he had the same MoBo already replaced a couple of times ... Kurt, et al, I have been following this VIA vs Linux thing for some time now. (My "big machine" is an Athlon based system. So it interests me.) Comments have been made about the size of power supply needed to keep these systems happy with 400 watts coming up in discussions frequently. But if you pause to think on it a few minutes you begin to wonder about this concept. The RAM runs at about 3.3 volts. The CPU core runs at about 1.7v (in my case.) So both of these are running off of power supplies on the motherboards that take the 5 volts down to something reasonable. If the problem is inadequate power supply AND it is more of a problem with some motherboards than others I look for the volts. Where are the losses which could cause this. One source is the connector from the power supply to the motherboard. (This was a chronic problem with A2000s, for example.) I don't see newer style connectors that have less contact resistance on any systems. That is probably a factor. Since the problem is greater with some boards than others I suspect that the auxilliary power sipplies on the motherboards are better for some boards than for others. Somebody with hardware access to a sufficient variety of mother- boards should survey this. Do they all use exactly the same power supply parts? Another issue is the speed of these systems. And the Athlon problem seems to peak when driving the various buses at their peaks. RF crosstalk is an issue that a lot of digital designers claim to understand when they design (and model) their circuits. Now, I built my first circuit analysis program back in about 1975. Results of that work fly on GPS satellites today. Since it was MY program I used for design I was acutely aware of its deficiencies as well as the modeling deficiencies. At some point in the analysis you cut a corner or two in order to make the calculations tractable. You do not manage to get all the "strays" into the models. What I ams saying is that board layout is another area where problems may exist. These are not thigs software settings in the VIA chips can cure. On another mailinglist catering to developers for very exotic video cards some problems with the latest INTEL based motherboards are appearing. (DigiSuite:E and its kith and kin drive the PCI bus very hard.) I suspect we have a situation not properly anticipated in modeling the backplanes on all these boards. And until the designers can wrap their minds around the entire problem the software solution may simply be, in the words of an old philospher, "Slow down! You move too fast." At the same time someone with suitable test equipment needs to look for voltage glitches out of the motherboard regulators and we need to develop software tools for "forcing" the suspected crosstalk and ideally characterising it with regards to data passing on the bus at the time of the bad data transfer. The software based fixes seem to be shooting at black cats in a coal mine without a flashlight or IR goggles. {^_^} Joanne Dow, jdow@earthlink.net