All of AMD's FX processors are unlocked, so overclocking them is, in theory, as easy as turning up the multiplier. I generally prefer to overclock my CPUs using the BIOS—err, firmware—rather than the various Windows programs out there. However, more recently, I've taken a liking to the ease and quickness of AMD's Overdrive utility, along with its ability to control Turbo Core behavior very precisely. So, when it came time to overclock the FX-8350, I decided to use Overdrive. I'm not sure it was the right call, but that's what I used.
When you're overclocking a CPU that starts out at 125W, you're gonna need some decent cooling. AMD recommends the big-ass FX water cooler we used to overlocked the FX-8150, but being incredibly lazy, I figured the Thermaltake Frio OCK pictured above, which was already mounted on the CPU, ought to suffice. After all, the radiator is just as large as the water cooler's, and the thing is rated to dissipate up to 240W. Also, I swear to you, there is plenty of room—more than an inch of clearance—between the CPU fan and the video card, even though it doesn't look like it in the picture above. Turns out the Frio OCK kept CPU temperatures in the mid 50° C range, even at full tilt, so I think it did its job well enough.
Trouble is, I didn't quite get the results I'd hoped. As usual, I logged my attempts at various settings as I went, and I've reproduced my notes below. I tested stability using a multithreaded Prime95 torture test. Notice that I took a very simple approach, only raising the voltage for the CPU itself, not for the VRMs or anything else. Perhaps that was the reason my attempts went like so:
4.8GHz, 1.475V - reboot
4.7GHz, 1.4875V - lock
4.6GHz, 1.525V - errors on multiple threads
4.6GHz, 1.5375V - errors with temps ~55C
4.6GHZ, 1.5375V, Turbo fan - stable with temps ~53.5C, eventually locked
4.6GHZ, 1.5375V, manual fan, 100% duty cycle at 50C - lock
4.6GHZ, 1.55V, manual fan, 100% duty cycle at 50C - crashes, temps ~54.6C
4.4GHz, 1.55V - ok
4.5GHz, 1.55V - ok, ~57C, 305W
4.5GHz, 1.475V - errors
4.5GHz, 1.525V - errors
4.5GHz, 1.5375V - OK, ~56C
At the end of the process, I could only squeeze an additional 500MHz out of the FX-8350 at 1.5375V, one notch down from the max voltage exposed in the Overdrive utility. AMD told reviewers to expect something closer to 5GHz, so apparently either I've failed or this particular chip just isn't very cooperative.
I disabled Turbo Core for my initial overclocking attempts, but once I'd established a solid base clock, I was able to grab a little more speed by creating a Turbo Core profile that ranged up to 4.8GHz at 1.55V. Here's how a pair of our benchmarks ran on the overclocked FX-8350.
A couple of other notes. First, remember that we measured peak power draw for the stock-clocked FX-8350 system at 196W in x264 encoding. The overclocked and overvolted config tested above peaked at about 262W, considerably more than the stock one. As you might imagine, when dealing with that sort of heat production, our Frio OCK was spun up like Joe Biden during the VP debate.
Second, I had hoped to include a quick Skyrim test to see how the FX-8350's gaming performance is improved by higher clock frequencies, but when I went to test it, our overclocked config wasn't entirely stable. The game didn't crash, but our character moved around erratically from time to time. (I'm straining to resist making a second Biden reference here.) We'll have to spend more time with the FX-8350 in order to find an optimal overclocked config.
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