Author: Aaron Gordon
Date: 01:16:24 07/03/03
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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. :) >I was hoping that the link provided would be some data from a production tester >showing that all chips are yielding at a certain speed, and just being marked >differently. This is possible, but has not been demonstrated. I have gotten this >type of data from DRAM developers in the past when I was developing a graphics >chip. (I forget what we did with that data.) It's obviously not something that >manufacturers give out to just anybody, especially if it would cause them to >lose money if it were widely known.
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