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Hard choices: Considering CPU Overclocking

Faster, Faster!

Featured post Some overclocking, yesterday.

When the artist previously known as Fingers McMeer – and my former PC Format paymaster from the good old days – first mooted some contributions to RPS on the matter of hardware, I was struck by a single, sobering thought. For the love of science, please don’t make me talk about overclocking. Here we are, then, talking about overclocking.

And you know what? It’s OK. Because what we’re going to tackle is real-world and worthwhile overclocking. Not the futile, fanboyish sort. In fact, when it comes to CPUs, it’s the sort of overclocking you really ought to be doing if you’re not already. Here’s why.

The background to all this comes in two parts. How the market as a whole got to where it is today, on the one hand, and how I came to own a pathological antagonism to a certain sort of overclocking twaddle, on the other.


Please make it stop.

The latter is easy enough to explain. I’ve simply sat through 27 too many pointless press events involving some hired lunatic hand, for some reason usually Scandinavian, demonstrating the latest chip running at a hitherto unprecedented and entirely irrelevant speed courtesy of liquid nitrogen.

It’s these very same people who buy £500 video cards, but don’t play games. Ghastly. Anyway, more important is understanding the currently patchy-going-on-parlous state of CPU overclocking.

As ever, much of it comes down to Intel, both for better and worse. The problem is Intel’s domination. Its chips are so much better than AMDs, it can get away with what amounts to antagonist behaviour towards its customers.

That means arbitrarily locking out features. Critically in this context, that includes access to the CPU multiplier. And it’s multiplier access you need these days to do any meaningful overclocking.

It’s actually a little more complicated than that. The most popular method of overclocking Intel chips used to be via the front side bus or base clock. This wasn’t a fully pain-free a method, but it did mean most chips in recent years could pony up pretty healthy overclocks, with 1GHz of extra frequency often a reasonable expectation.

And then came the Sandy Bridge generation of chips (which includes the RPS-favourite Intel Core i5-2500K) and the party was over. In simple terms, Intel shifted the clock generator from controlling just the CPU part of the chip to the whole shebang, including features that used be on the motherboard, like the PCI Express interface.


A rare overclockable chip from the evil empire.

The upshot of which is that Sandy Bridge processors and their Ivy Bridge successors fall over if you push the baseclock more that a couple of percentage points from stock. Which means the only option is the multiplier. And that’s something to which Intel chooses to ration access.

K Series and Extreme Edition chips are effectively fully unlocked while some mid range chips have very limited access to overclocking, typically what Intel describes as one “speed bin” or 200MHz to 300MHz depending on the chip in question. Some at the bottom have none at all.

You’ll also need to bear in mind that only certain Intel chipsets give you proper access to the multiplier. So, you’ll need to research that. If in doubt, buy a chipset with a Z or X in the title and you’ll be OK. It’s also true that overclocking mileage does vary between boards. It’s not often a dramatic difference, but the info is out there and easily accessible if you care enough.

With all that in mind, let’s assume you’ve got or are planning on buying a K Series model (if you haven’t, there’s not much to discuss – we’ll come to AMD chips momentarily). What should you be aiming to achieve and how should you go about it?

Well, you’ve got three options. Quick and dirty, which is frankly all the overclocking most people need and all I can personally be bothered with. Next is to use the motherboard’s auto overclocking options for a little help. Finally, it’s the full-on hand-tuned option.

The latter gives the best results, but is monumentally tedious and a classic example of diminishing returns. Don’t bother. Instead, keep it simple and start by jumping into the BIOS and whacking the thing up 500MHz. Then reboot and then repeat, but in 100MHz increments from there until falls over.


Are you afraid of the big, bad BIOS?

Now that the baseclock is a nice, even 100MHz, you do this by knocking up the multiplier one notch at a time (or five notches for that initial 500MHz fling). Precise methods vary, but typically involve flicking a blanket override switch in a branded overclocking menu from ‘auto’ to ‘manual’ to expose the multiplier settings. Google is your friend here, as I hope the comments below will be, too – let’s help each other out. Don’t worry about anything else. Odds are, you’ll get close to or maybe even better than a GHz’s worth of overclocking.

Once you’ve found a stable overclock, my view is that you should knock it back 200MHz and leave it like that forever. Gaming is pretty stressful on PCs, so you want a little margin in hand. But once you’re there, don’t worry about the temps or the power consumption. Life is too short. The odds of killing the chip as described are very remote indeed and the impact on your electricity bill is going to be slim to none.

The only other thing to think about and only if you’re really going for a big overclock is to use your board’s auto overclocking capability to help with voltages. Now, it’s often the case this happens automatically anyway – ie your board will automatically tweak voltages as you go along.

However, if you’re not sure, one option is to enable the full overclocking function that includes allowing the motherboard to do the lot including set the multiplier. The overall results will be mediocre, but the fringe benefit is the CPU voltage the board has come up with. It won’t be perfect for higher clocks, but it will be better than leaving it stock. Note it, put things back to manual and then plug in the new value.

And that really is it. Don’t bother with tweaking the memory, modern chips are bandwidth saturated, or any of the other voltage settings. It’s just not worth the bother.


It’s one big overclocking party over at AMD

If you’re wondering about AMD chips, most of the above applies. The difference is that as the underdog, AMD uses unlocking as a sweetener to tip the balance in its favour. So you’ll find all manner of unlocked AMD chips along with fewer, if any, motherboard restrictions.

Indeed, as this price list shows, every single retail example of the AMD FX processor is a Black Edition and thus unlocked. Just bear in mind that overclocking mileage varies a bit more from model to model with AMD chips. You’re not going to get an extra gig out many FX chips. Well, not unless they’ve really improved things since last I had a play with a hand-picked sample.

Oh, and before I forget, cooling. This isn’t absolutely critical, but you can get a really nice air cooler for just £30 or so. Personally, I think it’s a a worthwhile punt as you’ll be able to reuse it for multiple systems.

Go for anything from a decent brand like Enermax or Corsair with a 120mm. Job done. For those who need hand holding, buy this one. I recently spent a weekend with 12 coolers. One of the worst weekends of my life, if you must know. And then I ended up writing up half of them on holiday in France. All somewhat self inflicted. But I digress. That was the best of the bunch.


The Enermax cooler. Think not. Just buy.

Meanwhile, do not buy one without a fan thinking the silence will be golden. It’s not suitable for gaming. You won’t kill your rig, but you will find the CPU thermal throttles. Not good.

As for water cooling, it won’t buy you much additional frequency for the sort of overclocking we’re talking about and it costs a lot more. It does reduce temps, but honestly, so what? If your cooler’s seated correctly and you’re not running the thing on the ragged edge, because I’ve already told you not to, you’ll be just fine. That said, and to flatly contradict myself, if you’ve money to burn, the latest water coolers are utterly painless, zero maintenance things, so I wouldn’t blame you.

So there you have it. Overclocking ain’t what it used to be, sadly. You can no longer buy a poverty chip and clock it up to flagship speeds. But if you do have a K Series Intel chip, you’d be bonkers not to ramp it up at least 500MHz or so. There really is no downside. A £30 quid cooler and all of a few minutes in the BIOS for free performance and no downsides. Like Arnie said, do it. Do it now.

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Jeremy Laird

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