Just registered to say thanks to Jan Kivar for an excellent article. I decided to have a go with CrystalCPUID and it payed great dividends in terms of reduced heat and fan noise.
I am using a laptop, Aspire 1362WLMi, AMD Sempron 2800+ (SMN2800BIX3AY). The default Cool 'n' Quiet steps were 800MHz @ 0.95V and 1600MHz @ 1.4V. It is now running 800MHz @ 0.8V and 1600MHz @ 1.075V. Seems stable at both speeds, though they've only been checked under Prime95 for a couple of hours. Under normal use, the temperature is so much lower that the fan is now off for most of the time; nearly as good as a new machine
My only concern is that if
the CPU falls over through undervolting, I won't be able to reboot without resetting the CMOS (there's a warning on this at the start of the article). As it's a laptop, I really don't want to have to dismantle it to reset. Can anyone reassure me how likely this is? I'm hoping that a straightforward reboot would be enough to unlock a frozen system (I haven't set CrystalCPUID to begin on startup).
I think this Sempron has two speed steps by default; would it be possible to run with three steps, having the multipliers set at, say, 4, 6, and 8? It appeared to work with three steps at different voltages, but with the same 8 multiplier on the higher pair of voltages. Just don't want to fry it if it's not supported.
Lastly, great forum! Wish I'd found it earlier.