Low Clock High Multi vs Higher Clock lower Multi on 2600K

dynamis_dk · 22 Apr 2011 at 12:34

I've been playing for the first time yesterday and i've managed 5Ghz out of my 2600K so i'm pretty happy.

I was wondering today, what is anything is the difference in using a lower clock speed and a higher multi, vs using a higher clock and lower multi to achinve the same overall cpu clock speed. I.E....

100 x 48 = 4800Mhz
96 x 50 = 4800Mhz

I went down the higher clock (what i would understand to be like fsb speed) and lower multi to try and get my ram running as close to the 2000Mhz mark as i could.

What would be the effect of underclocking the bus and using a higher multi to get the same total cpu mhz... would the ram be running slower and benching would suffer??

JonJ678 · 22 Apr 2011 at 12:52

Everything runs at a multiple of the bsck. A higher bsck generally means higher ram speeds, though you can change the multiplier there as well.

The difference is likely to be negligible, but a lower cpu multiplier for the same overall frequency tends to mean higher performance, as the ram, imc and other circuitry I haven't heard of are then running at a higher frequency.

edit: I'm assuming you've done more stability testing than the 150s run shown in the screenshot. If you haven't, make sure the current 5ghz is stable before trying to optimise further

Surveyor · 22 Apr 2011 at 13:05

A bit irrelevant with Sandybridge as you're not supposed to overclock using the base clock.

Do not overclock with BCLK, doing so could limit lifespan of the CPU

Adjusting the base clock affects your whole system as everything (USB, SATA, PCI, PCI-E, CPU cores, Uncore, memory etc.) is all linked to the base clock. So you shouldn't increase or decrease it from 100MHz.

JonJ678 · 22 Apr 2011 at 13:08

Ah, damn. I was assuming that the bsck = 100 thing was on the early revision boards, and no longer applicable. That's a strange quirk to be intentional.

Apologies OP, I should think more carefully before typing.

Surveyor · 22 Apr 2011 at 13:12

JonJ678 said:
Ah, damn. I was assuming that the bsck = 100 thing was on the early revision boards, and no longer applicable. That's a strange quirk to be intentional.

Apologies OP, I should think more carefully before typing.

It's intentional because it means Intel can sell processors with unlocked multipliers for more money as these are now the only ones which can be overclocked.

You can't just buy any Sandybridge processor and overclock it.

dynamis_dk · 22 Apr 2011 at 14:17

Cheers.

I had previously been told to be careful clocking it upwards but I was just wondering on the effect.

The run I did above was purely to hit 5ghz and do a prime run. I've clock I back to 4600 @ 100 for 24/7 duties. Moved from a Q6600 setup so even stock speed on the 2600k are hugely better then my previous system.

Thanks guys

Disco Boy · 22 Apr 2011 at 14:30

1.48V?! Are you intending to keep running it at that voltage? If so then don't expect it to last for very long.

dynamis_dk · 22 Apr 2011 at 14:49

Ah no, like above those setting were just to push and do a benching run. Am back down to 1.3 now @ 4.6ghz. Need to tweak it later to settle in my final 24/7 setup but it won't be 1.4+