Cool?N?Quiet - how exactly does it work

[Speedo]

As I understand it, multipliers and core voltage is changed dynamically? How do the function define when more power is needed? How does it work in combination with overclocking?

 

[Budman]

http://www.amd.com/us-en/assets/content...s/Cool_N_Quiet_Installation_Guide3.pdf


http://www.amd.com/us-en/Processors/Pro...on/0,,30_118_9485_9487%5E10272,00.html

 

[otispunkmeyer]

it works in overclocking yes, all it does is reduce the voltage and the multiplier down to 4 or 5, thats it. so if u overclock a 2Ghz to 2.2Ghz
cool n quiet will go from 1000mhz to 1100mhz

 

[Speedo]

Are there any obvious drawbacks with having it enabled? Are the jumps between low/high speed truly transparent to applications?

 

[Icepick]

Be careful if you use Cool n' Quiet while overclocking. It's perfectly safe if all you're doing is adjusting the FSB to increase the CPU speed.

BUT, you'll have big problems if you try to overclock by lowering the CPU multiplier. When C'n'Q kicks in it lowers the multiplier to around 5 and the CPU voltage is lowered along with it. When you fire up a game or some CPU intensive application C'n'Q will raise the multiplier up to the default stock setting and ignores the multiplier you set in BIOS.

If you're running a 3200+ and overclocking to 2.5GHz by raising the FSB to 250 and keeping the multiplier at 10 you'll be fine.

If you overclock a 3200+ at, say, 2475 by raising the FSB to 275 and lowering the multiplier to 9 then you'll have a problem. When C'n'Q ramps up the multiplier it will put it back to 10 (default). The CPU speed will now be running at 10*275=2750MHz. The system will most definitely crash.

 

[MrControversial]

Nice info there.

 

[stackingreasyBBs]

Does it mess with the HTT multi in the same way? ie putting it back to default? Cause it would sure cause problems if you were accidentally running 275FSB and a 5x HTT multi.

 

[TheGlassman]

C'nQ will crash the system (when attempting to reduce voltage to under clock) most boards if voltages are set manually. Multi will go to what is set in bion,ie will not restore an 11x if 10x is set and Htt multi is uneffected.
Basically I'm saying if you leave cpu voltages at default (auto) you can overclock and use Cool 'n Quiet, but higher overclocks that require more voltage to be stable will not work. C'n Q is worthless on a desk top so why bother with it.

 

[imported_JohnC]

I think that could vary by motherboard. When I tried to oc and had voltage set to +0.1v, CnQ would drop the voltage to about from 1.45v -> 1.15v instead of 1.35->1.05v like it usually is. Also my mobo doesn't allow the multiplier to be set if CnQ is turned on. Using an Epox 9NDA3J.

 

[Icepick]

Originally posted by: stackingreasyBBs
Does it mess with the HTT multi in the same way? ie putting it back to default? Cause it would sure cause problems if you were accidentally running 275FSB and a 5x HTT multi.

No, it only changes the CPU Multiplier. The HTT multiplier will remain whatever you have manually set in BIOS.

 

[Speedo]

Thanks a lot for all the info. It sounds as if it's recommended to run when overclocking. And I agree that this function is probably mostly useful with laptops, bu tit could also be nice for periods when you are mostly surfing etc. But since it does not seem to affect fans, Q-fan might be a better idea. It seems to work well, and I like the fact that you can set a target temperature. I haven't tried to see how the fan spins up when the target temp is reached, but i assume there are only two fan speed modes?