The Problem with Overclocking

Written by Clive Webster

December 21, 2009 // 10:50 a.m.

Tags: #cpu #intel #issue #overclocking #problem #processor

For some completely unknown reason (alright, just one I can’t tell you yet), I’ve spent most of last week testing and overclocking CPUs. Because of the way the magazine deadlines work in the run-up to Christmas, deadlines are tight, but the urge to get the very last MHz from a CPU still bit me pretty hard. [break]

One of the CPUs I was testing was a Core 2 Duo E7400 – we’d previously seen that the E7300 could overclock from 2.66GHz to 4.2GHz, and I was sure I could 4.3GHz out of it. In fact, I initially tried for 4.4GHz but just couldn’t get the second core stable under Prime. Nothing I tried could get that second core to play ball – the worker thread on Prime95 crashed out the moment I kicked in the smallfft test.

Normally we head off home at 6pm (we start at 10am, so it’s still an eight hour day) but here I was at ten to eight in the evening tapping numbers into my calculator, determined to get 4.3GHz out of the chip. I was played with the GTL for the second core, trying various combinations of PLL and vcore and generally trying everything I could to get that troublesome second core to work. Finally, after many restarts and failed attempts, I conceded that 4.3GHz wasn’t possible.

I quickly verified that 4.2GHz was fine, and, glancing at my watch to see it was now past 8pm, I tried to get the bloody CPU as close to 4.3GHz as possible. Why? Why did I do that? What difference was it going to make to any benchmark – let alone the review itself – if the CPU was clocked at 4.25GHz or 4.28GHz? What was I going to prove? I took me five or six further failed attempts to realise that actually the CPU wasn’t going to go any higher and I should settle for 4.25GHz.

The weird thing is, a few of years ago I’d have been thoroughly chuffed with a 52 per cent overclock for two hours of BIOS fiddling. The other night it just felt like a failure… This is just one of the many problems with overclocking, but my sleep-deprived, blood-shot left eye makes this particular issue the most annoying. Where do you draw the line between a worthwhile amount of performance gains for the time you've invested?