Are you asking on the efficiency of a PSU affecting the CPU? It has no effect. The efficiency of a PSU is a measure of how much power is drawn from the grid relative to how much power the PSU distributes. A PSU that's using 300 watts of power and 80% efficient means 300/0.8 or 375 watts of power is drawn from the grid and you pay for that 375. Whether the PSU is 30% efficient or 99% efficient, it has no effect on the CPU.
4.5 GHz will be about 12.5% faster than 4 GHz. When overclocking, be sure to monitor your temps - don't let them exceed 70C for Intel, 60C for AMD.
I doubt that temperature affects speed. It's only when temps exceed a certain point that it starts becoming troublesome. Put a CPU in an environment of -200C and you could probably overclock a 2600K to 7 GHz just fine, motherboard and voltage permitting. You'll only find such a setup in laboratory environments though.
"running at 4.6 Ghz" means it is running at 4.6 Ghz and will always be faster than 4.0 Ghz regardless of temperatures......Now that is different from saying "set to run at 4.6Ghz" as if the CPU is running hot and is throttled because of the heat, then it is in fact "not running at 4 Ghz".
SB can run a lot hotter than the ole 9xx series though many peeps still like to keep temps below 72C .... that's not what Intel says tho:
I have tested my 2500K and it auto-throttles before the temps actually reach the maximum. The maximum safe temp is 98ºC, but it auto-throttles in the low-90sºC.
Again as published by Intel, TJMax for Sandybridge is 98C ..... Note CoreTemps are a very different number than Tcase which IIRC Intel published at 72.6C.....Intel doesn't quote a mac acceptable core temp but 85C is the most commonly quoted core temp max
For 24/7 usage, I'm at 62-68 on the cores of a 2600k at 4.6 GHz, HT and all other BIOS settings enabled......jumping 0.2 GHz req'd a voltage bump to 1.4 (from 1.36) on my 1st attempt and temps jumped to 69-79 which I was not comfy with .... turning off HT dropped them 7-10C......I wanted to work on it further but, my son was patient enough letting me experiment with his new build and despite 6 months or so going by, I haven't been able to get him off the thing long enough to do any more "experimenting". I did create a 5.0 Ghz BIOS profile which was stable under P95 but last time I was able to sneak on the thing it BSOD's and by time I rebooted, I got chased off
I'm talking efficiency as in CPU speed. Computer parts run faster when they are colder, but by how much is what i was asking.
I think you have misunderstood "Computer parts run faster when they are colder". It is NOT an "efficiency bonus".
What it means is that if you can keep the CPU at 40 degrees, you can overclock it further. At 60 degrees it might fail at 4.5GHz, whereas at 40 degrees it might not fail until 5GHz (or more). So it you put a better cooler on it, you may get a better overclock. That's why you seen insane speeds being achieved using chilled water (or liquid nitrogen!) cooling - it's not that the part is more efficient, it's that it can be over-clocked further.