(Answer) (Category) distributed.net Faq-O-Matic : (Category) the Client software : (Answer) Is overclocking good to do?
Overclocking has been known to cause your machine to become more unstable, more prone to crashing, produce greater heat, and shorten the life of your processor. Furthermore, it is known to cause programs to unreliably execute code correctly, resulting in occasionally incorrect calculations. This includes the functioning of the distributed.net client.

(Remember that even one miscomputed key within a block, that happened to contain the key we are looking for, can ruin the entire project and invalidate the work of the hundreds of thousands of other participants if an entire re-check must be done.)

Furthermore, because the distributed.net client fully utilizes your processor and keeps it continuously busy, your processor will generate more heat than it would if it were completely idle. For systems that are properly designed to incorporate sufficient cooling, this should not be a problem at all. However, for machines with inadequate or broken/failing fans this may cause a buildup of heat, causing the same malfunctioning that may occur in overclocking environments.

Even running the built-in "test" functionality within the client may not be sufficient to detect such occasional failures, since the failures may only occur after a sufficient amount of heat has already built up. It might be beneficial to run your client with disabled networking for a few hours (so that it will not transmit back any potentially bad blocks), and then quickly stop the client and activate its "test" function to see if that reveals any problems. However, although we try to be thorough in the "test", it may still not detect all occasional CPU malfunctionings due to heat stress.

In summary, we highly recommend not overclocking at all. However, if you feel you must, it is probably not best to overclock to the very verge of crash tolerence--one or two steps below your systems operational maximum might be a better choice. Either way, please be sure to have *more* than sufficient cooling.

Note that AMD processors generally, and the K6 series in particular have lower heat tolerance than, say, Intel processors, and have a tendancy to overheat even without overclocking. Numerous "bug" reports about the client causing the whole system to become unstable have been reported (See bug #200, #242, #1262, #1276, #1300,...), which is of course not the clients fault at all.

When a processor is overclocked, there are actually two issues that can cause malfunctioning: The first issue is insufficient electricity--if a processor is overclocked by 15%-50% (depends on the processor) it may not operate correctly, to avoid that you need to increase voltage, and this makes a processor HOT. The second issue is therefore the heat build-up caused by increased voltage (and also increased frequency), so you need an extra heatsink or fan or both.

RC5-64 is a serious project that demands RELIABILITY, and it would be a good idea to run the processor at the speed it was designed to run.

I also have found that on many motherboards the overheat will cause a processor slowdown of around 50-100-150MHZ until it cools off. The interesting part is if you are running Windows NT, Linux, FreeBSD, etc you won't notice much until you install dnetc, since the OS runs "HLT" instructions which cool the processor during idle cycles. When dnetc is running it cannot do that, so it overheats, slows down, and your block rate gets really sucky. It is really a terrible idea to do it just for dnetc. If you do it for other reasons, keep an eye on the temperature. Please don't make all my and other's work in vain by screwing up the contest!
Front line report of errors caused by overclocking: http://blogs.msdn.com/oldnewthing/archive/2005/04/12/407562.aspx
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