Is my 3.55 ghz overclock better than 3.75 on core i7?

[nonxcarbonx]

You would normally take the higher overclock, but the 3.55 got 9:50 super pi while 3.75 got slightly above 10 minutes, and is 10 degrees hotter. I figure the drop in supposed performance is due to using a x8 RAM multiplier for 3.55, and a x6 for the 3.75. I figure I'll probably keep the 3.55, but I was wondering if the 3.75 speed is actually better. Any thoughts?

 

[the last resort]

personally, gaining 200 mhz and running 10 degrees hotter is not worth it. I can tell you that the efficiency of the processor dropped, and is pulling much more power. IMO 3.55 is plenty most people. However, 3.75 could mean bragging rights, and not necessarily a real world imporvement.

 

[eklipz330]

try some other benchmarks... i see dips like that as well, it gets quite strange

 

[cjl]

The reason is probably because SuperPi loves RAM speed. The 3.75 is probably faster on many tasks, but for a 10 degree difference in temps, I'd take the slower, cooler one almost every time.

 

[rambo117]

There is an estimated 3 percent improvement for every 10 degrees celcius that the cpu temp goes down.

That works both ways
i.e. every 10 degree increase in temperature would result in a 3 percent decrease in performance.

then what happens when you use LN2?

😛

 

[jsrudd]

Is this a case of turbo mode kicking in or do you have that disabled? If I remember at high Ghz the i7 will actually self throttle because of heat.

 

[nonxcarbonx]

Turbo is enabled, but it doesn't make much of a difference. It's at 70 degrees at 3.55 and 80 at 3.75. I tried 4 ghz just to see if I could get it, and with 1.5 v core v, 1.36 vtt it still only was in windows for a few seconds before bsod. It seems to take alot of voltage, even for CO stepping.

 

[Scotteq]

80 degrees is too hot, IMHO - LIkely the decrease in performance at the higher speed is due to throttling.

 

[cjl]

Likely not. Throttling on i7 doesn't occur until well past 90C. I'd bet that your memory is running faster with the slower CPU clock setting due to memory multipliers, and that is the reason. I also bet that there are other benchmarks that would show the faster setting as being faster.

 

[one-shot]

With an ambient temp of around ~20C, my i7 @ 3.6GHz with 8 threads never goes above 70C for the CPU and around 75C for the cores. the ~68C thermal spec for the i7 set by Intel is for the IHS, not the cores, as the cores will generally be 5 degree C over the CPU temp. I also put a better fan on my CPU cooler that moves much more air. My i7 @ 3.6Ghz with HT is more desirable for me than 3.7Ghz without HT/SMT on. Turbo off, of course.