Underclocking SB cpu - need some advice

MrM · 22 Mar 2011 at 21:08

After calling OCUK today and speaking to a nice fellow who made me think of underclocking an SB chip, I have some questions and would be grateful for your thoughts.

Background is I am looking to build a new desktop, but with a catch. It needs to fit in an HTPC case. I would say it will be an HTPC except it will be doing a little bit of photo editing, ripping and encoding, so needs a bit of grunt. Budget not an issue.

So... Ive been waiting for an i5 2500s or i7 2600s since the chips were announced. But only the 2400s has made an appearance at retailers.

Ive also been waiting for the B3 revisions of the Asrock H67 boards, as they seem to be the only boards that state they output HDMI 1.4a (3D). They also do a HT PC specific one, with THX sound output which would be a bonus.

Ive been waiting for this combo for months, but they dont show, so Im now thinking of alternatives. Im keen to reduce clutter in the rig, and it wont be used as a gaming machine, so the onboard GPU in SB appeals.

This is when the gentleman I spoke to at OCUK put me onto getting a standard SB chip, underclocking it and reducing voltage to mimic the S models, and a quick google suggests similar TDP rating to an S chip can be ahieved. He claimed that the H67 board allowed underclocking but not overclocking. Regardless, he gave the the impression that a Corsair H50 would cool a 95w TDP 2500 / K easily anyway, and would be dead quiet, so would suit my situation underclocking or not. I know the K in an H67 is deemed a waste by nany, but as I understnd it, the K comes with better on board graphics, which would justify the premium, even if I were to bizarrely underclock this chip.

So does anyone have any experience of underclockig SB chips on an H67, or any advice to offer?

Many thanks

MrM · 23 Mar 2011 at 20:50

Anyone have any experience?

Cookeh · 23 Mar 2011 at 20:54

Really don't need SB for an HTPC - even if it's doing some photo editing.

Underclocking SB is completely pointless anyway, defeats the purpose of having a fast, high clocking chip.

Sounds like OcUK is trying to milk you :rolleyes:

MrM · 24 Mar 2011 at 08:22

Then maybe I am their ideal customer. Like I said, budget not an issue, the SB option works well for me, as it means I dont need to buy a discreet graphics card in what is going to be a very small and compact space.

The whole point of underclocking is because Ive been waiting for forever and a day for the 2500S to come out....

Hagar · 24 Mar 2011 at 08:30

Sounds like a plan. After all if you have this CPU you can always put it into another machine or sell it on if you decide to buy the s version later. You get the sandybridge technology rather than compromising on an older socket and I would try to get a passive cooling system from it as you are underclocking. It is possible that just undervolting will sufffice.

MrM · 24 Mar 2011 at 09:36

Glad to see at least one other person doesnt thing Im talking utter nonsense.

The benefit of the 2500K, as I have been reading, is you get the better on board graphic card chip over the S, which would be another benefit.

And thats what I plan to do, undervolt and underclock.

The case will be inside an AV rack, with not that much space surrounding it, so airflow is a concern. The chap at OCUK recommended the Corsair H50 kit, which should fit inside the case no problem, and the advantage that this will also give me, is that Ill be pumping out any head direct to the outside, rather than having it festering inside. May seem like overkill, but I think theres some method to the madness.

My one oustanding question is whether H67 boards will let you underclock. I know you cant overclock, but Ive not read anything concrete as to underclocking.

Hagar · 24 Mar 2011 at 10:41

I have underclocked several CPU's from reasons of absolute silence to making sealed prototypes for use underground.

I have looked for examples of underclocking but Intels strange restrictions on the '67 chipsets and my lack of knowledge of UEFI Bios means I cannot be too sure.

I would have thought that you should be able to fix the CPU speed down to the lower bounds of speedstep, disable turbo and also reduce the 100MHz clock to something a bit less although the latter may reduce graphics performance a bit.

There is a software OC app from Asrock, I do not know how capable that would be for underclocking.

I would email them direct for the bus and multiplier ranges of adjustment.