Faster RAM = Higher CPU Temps ?

[Buraq]

Last night I read until my face was flat on my desk. I have 4 stick of 2GB 8500C5D memory that runs 1066Mhz. Whenever OCing my Phenom 955 to 3.7Ghz my temps would hit 57c on Prime95 full load with ambient temps of 75f. I could never get 3.8GHz and not go over max temps of this CPU.

 

I dropped my RAM freq back to default 800Mhz and tightened the timing to 4-4-4-13 and my temps of 3.8Ghz OC dropped about 10c ? Huh !? So now I can run 3.8Ghz OC with RAM at 800Mhz @ 52c-55c on full load with Primte95. Btw my CPU water block is a piece of crap Thermaltake W1. My Koolance CPU-350AC water block just got delivered to my home today, so I will be installing it later that will for a fact deliver lower temps. I dropped the RAM speed even further to 667Mhz and my temps dropped to 48c-52c on full load with Prime95.

 

Now hear is whats even more weird. My CPU score on Avantage was high with RAM speed at 667Mhz ? My head starts hurting here cause the 8500C5D is rated 1066 but I was getting higher CPU scores running the Ram at 667 though @ 3.8Ghz OC with significant lower temps ?

 

Was I OCing my CPU wrong the whole time ?

 

From what I am gathering here is if your running higher RAM speeds your CPU will have less head room for OCing ? 3.7Ghs was the border line and 3.6Ghs OC was for sure safe zone running the Ram speeds at 1066.

[AIinc]

Prime95 is ok for testing your cpu, but IMO it's basically a great memory tester.

Try the Intel Burn In test, and stress your cpu.

Or use the OCCT stress test, set it to custom, and then set it to test the cpu, and not a mix test.

 

Both of those will heat up your cpu, and give you a better full load cpu test.

 

I'm not real familiar with AMD cpu's, but the memory controller may be the cause of your higher temps when running your memory at it's stock rated speed (1066MHz)? Don't know. It may run cooler when your putting less stress on the memory controller? If thats the case, then hey, cool! You have a stable 3.8GHz.

 

Hopefully a more experienced AMD owner will come along with better help for ya!

I know there's a lot of Phenom 955 rigs here at OCC.

 

BTW...nice rig!

 

Best of luck to you!

Inteller

Edited September 11, 2009 by Inteller

[ccokeman]

Prime 95 hits the memory bus as well as the CPU on the blend test and does a darn fine job of making sure you are stable. I would surmise the reason that you get hotter with the memory running faster is that it works the IMC harder with that 8GB of memory at a higher bus speed.

[Fight Game]

the heat from the memory itself couldn't possibly be transefering to the cpu with the water cooling, so it would have to be the memory controller on the cpu itself.

[Waco]

the heat from the memory itself couldn't possibly be transefering to the cpu with the water cooling, so it would have to be the memory controller on the cpu itself.

The heat from the memory isn't going to be enough to affect the temps of anything really...

 

I second the notion that the memory controller is getting hotter at higher speeds. That makes sense considering that the faster you switch a CMOS circuit the more energy you bleed in the transition.

[Fight Game]

ya, I tend to agree but I did have some ram once that I overclocked to hell, was damn hot, right next to my stock cooled cpu, and thought maybe it was affecting the cpu temp. And in that case, the memory controller was not on the cpu, so I guess it could have been the hot gpu, northbridge, ie ambient temp of the case. And I think you 4th'd the notion, hehe

Edited September 11, 2009 by Fight Game

[Buraq]

Thanks for the replies all. The memory controller sounds more like the issue as suggested. I bounced over to the Corsair forum and the Ram Guy suggested in a post if you want to run 2GB x 4 8500C5D DDR2 memory they should be ran at 800Mhz and not 1066Mhz with 4 sticks. Also running 4 sticks at timing 4-4-4-13 2T 800Mhz would be the same as 5-5-5-15 1066Mhz (I think I remember reading this) as in regards to speed.

 

The default clock on the Dominators with my Mobo are 800mhz but are rated 1066mhz.

 

I got my new Koolance CPU-350AC water block (& 1/2" tubing) @ 3.8Ghz with 43c-45c temps full load on prime95. After playing about 2 hours of Crysis temps are 39c-42c.

 

I got it to 3.9Mhz but it needed 1.55v to be stable with 45c-48c temps. Just cant get 4.0Ghz stable and cooling is not the issue anymore and alos I would be going over the max voltage for the Phenom.