Phenom II x4 945/955

[alikum]

Hello guys, this is a discussion for AMD CPUs. I am building a new rig to either have 945 or 955 very soon. Please do not recommend i5 or anything else. The choice is between these two stated in the title.

Now, I have Corsair TX650 and I intend to purchase two 5770s to crossfire. Is CPU overclock necessary for the 5770s to scale well? If so, which is a better buy? I know that 955 has unlocked multiplier but as far as I understand, overclocking by adjusting the multiplier will render Cool 'n' Quiet unusable, meaning that I can save energy at idle. On contrary, I know that 945, without unlocked multiplier, cannot go too far. I may be wrong but the discussion is open. So, please guys, make yourself at home ... Thank you in advance.

 

[HibyPrime]

You wont HAVE to overclock with those processors, but it will definitely help.

The 955 will make it easier to overclock, and will probably be able to hit a few hundred MHz higher than the 945, but we're talking about the difference between 3.9GHz and 3.6GHz kind of thing here - if you're overclocking that high then the choice is already made for you.

http://www.tomshardware.com/reviews/amd-enthusiast-crossfire,2421.html The CPU they used here and the overclocking might help your decision.

 

[alikum]

If I were to overclock with multiplier, Cool 'n' Quiet will be rendered useless, am I correct? That means that in the long run, I suffer a great loss (of electricity). Do correct me if I am wrong.

 

[XD_dued]

From what i've experienced, you can run cool 'n' quiet on an overclock, but it will decrease performance...very slightly, might as well be negligible. Just find max clock with cool and quiet off, then turn it on when you're done, and see if it is still stable.

 

[HibyPrime]

I'm not 100% sure if cool n quiet runs on higher multipliers, but I can say that even if it costs you a difference of 50W (which it wont, it'll be more like 10-20W) you're going to be loosing $3.60 a month @ 10cents/kW. The over clock it self is going to cost you a lot more than the loss of cool n quiet.

I know for a fact you can run cool n quiet when you turn up the base clock, but google would probably help with the multiplier question.

Edit: that dollar figure assumes you're running the computer idle 24/7, meaning never off but also never doing anything.

 

[loneninja]

Cool n Quiet functions fine on 2 Biostar motherboards I own when I overclock using the multiplier, but with a Gigabyte motherboard as soon as I adjust any overclock settings the BIOS automatically disables cool n quiet.

 

[alikum]

Oops, sorry I didn't list out my mobo. I have MSI 790GX-G65.