Author: enrico carrisco
Date: 17:03:24 07/03/03
Go up one level in this thread
On July 03, 2003 at 04:26:09, Sune Fischer wrote: >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. By this criterion, how do you know that your CPU is stable? Sure, it's probably not overclocked, but as you say: "I think it is possible for a chip to malfunction long before it actually causes a system crash..." What tests do you run to verify that it has come stable from the manufacturer? -elc.
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