Author: Sune Fischer
Date: 01:26:09 07/03/03
Go up one level in this thread
On July 03, 2003 at 04:16:24, Aaron Gordon wrote: >On July 02, 2003 at 20:55:52, Keith Evans wrote: > >>On July 02, 2003 at 20:18:25, Sune Fischer wrote: >> >>>On July 02, 2003 at 19:37:46, Aaron Gordon wrote: >>>>You can test how close they are to the limit. Please read: >>>>http://www.talkchess.com/forums/1/message.html?304354 >>> >>>You make it sound like you can state things with 100% certainty :) >>>What you are doing is not exact science, it's more of an ad hoc, "oh seems to be >>>working fine" experiment, IMO. >>> >>>This may be sufficient in many cases, I can't say it ever worked for me 100% >>>though. >>> >> >>He does not know the worst case path through the chip, and hopes that it is >>being exercised. The guys who wrote the BurnK7 program state that it is not a >>sufficient test. Basically if you run that and you have problems - then you know >>that you have problems. But if you run that and you don't have noticible >>problems, then you may or may not have problems. >> >>For example let's say that a certain ALU operation has a long delay due to the >>number of combinatorial gates in the path. Maybe this is what determines the >>maximum chip operating frequency. Well if you don't test this one operation you >>may think that the chip is fine because all of the other operations will work. >>Now you raise the temperature or frequency and the other operations start >>failing. So you think "wow I was close to the edge", but in reality you were >>over the edge and you just didn't know it. > >You can figure out how on-edge you are by doing the tests. Then as I stated in >my previous post you can kick the voltage up, drop the cpu temp to 'average' >levels, and clock back and get a 100% stable CPU. There are some production cpus >that can't run more than 5% over stock speed without producing the same >instability as one of the pretested chips I have running on-edge. I however back >off a good 10-15%, Intel (some P4-3.06s for example) only backs off about 5%. >This is too close for me. At least with my chips I know they're 100% stable. :) We may disagree on what instability is. I think it is possible for a chip to malfunction long before it actually causes a system crash, just like a piece of software can have many bugs that only rarely shows themselves. If you don't somehow very that _all_ of the CPU is operating perfectly, but only focuses on a few instructions, then the test is not sufficient IMO. How long would it take you to discover if 1 in a billion fpu operations are in error because of OC'ing, when the rest of the chip is operating perfectly? -S.
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