Overclocking And Platform Compatibility
Overclocking
Although AMD’s CPUs haven’t been the fastest for years now, the company continues to nurture enthusiast support through products that give power users certain features important to them. Software able to manipulate configuration settings in real-time on the Windows desktop, unlocked ratio multipliers, and platforms with far more PCI Express connectivity than the competition are just a few of the nods AMD gives to the folks who know and appreciate how each of those capabilities can improve platform performance.
The same overclockers who might have been disappointed in the scalability of AMD’s Zambezi-based FX CPUs using mainstream cooling might have something to get excited about this time around, even though we’re looking at a very similar architecture manufactured on the same 32 nm node.
Using a 1.375 V CPU voltage and a 1.175 V northbridge voltage, I was able to get FX-8350 running stably at 4.8 GHz under full load. In the screen capture above, I'm running a single-threaded test to spin the chip up, but the highlighted maximum temperature is where our benchmark suite peaked.
The FX-8350 wanted to go even faster, but the key here is a voltage setting low enough that you avoid hitting 70 degrees Celsius. At that point, the thermal monitor starts cycling cores to throttle down (evidenced in the image above), keeping the chip from getting any hotter and negatively impacting performance. So long as I didn’t trigger any threaded workloads, I was even able to run benchmarks as high as 5.125 GHz (requiring a 1.4375 V CPU voltage and 1.2 V northbridge setting).
Clearly, cooling capacity is going to be a bottleneck for most folks. I find AMD’s reference heat sink and fan to be dismally insufficient, and a beefy third-party upgrade is going to add to the FX’s cost. But, for the sake of testing, I used the closed-loop liquid cooler AMD offered with its FX processors last year to reach those overclocks. Something comparable will run you $70 or so. At that point, you’d probably want to consider a Core i7-3770 for $300 as an alternative. Fortunately, I have a -3770K in our benchmark results.
Overclocking to 4.8 GHz is enough to put the FX-8350 ahead of Intel's Core i7-3770 in a threaded workload like 3ds Max 2012, but it's not going to help AMD's Piledriver architecture overcome Ivy Bridge in a single-threaded test like iTunes. Of course, if you're willing to spend an extra $30 on a Core i7-3770K and even more on an aftermarket cooler, you can take the 3.5 GHz CPU to 4.5 GHz relatively easily and flip the script on AMD's overclocked FX, too.
Compatibility
All four Piledriver-based FX chips are compatible with the existing Socket AM3+ interface. Current FX-enabled motherboards need a BIOS update to recognize the new processors. However, boards that previously exhibited trouble with FX processors probably won’t get fixed. Asus’ Crosshair IV Formula, for example, should work with Bulldozer-based CPUs by AMD’s own claims.
Asus did add experimental support for the FX family back in 2011. However, the company never rolled in the update needed to stop a severe BSOD issue. As a result, many older AM3 platforms expected to properly support FX don’t, and we expect those problems to persist with Piledriver. We’ve heard assurances from AMD that the issue isn’t widespread, and that motherboard vendors are able to resolve it with an update. But certain manufacturers can’t seem to be bothered to bring older products up to date. Complaints about the Crosshair IV Formula and other motherboards are chronicled in this thread.
