AMD A8-3870K

There's good news and less-good news about AMD's new A8-3870K Accelerated Processing Unit (or APU). The good news is that it surpasses its predecessor, the A8-3850, in every way (if only slightly),
and provides overclocking features and performance potential beyond what you may think you can expect from a chip with a $135 (list) price?whether from AMD or Intel. But for all the strides AMD has made since it released the previous APU this past summer, the A8-3870K still can't replace a solid CPU?discrete video card combo for even quasi-serious gamers. But it shows that AMD is taking its Fusion product seriously, and thus hints at more good things to come.

Like the A8-3850, the A8-3870K is based on a 32nm production process and contains four CPU cores and a DirectX 11 (DX11)?supporting Radeon HD 6550D GPU with 400 GPU cores (in roughly the middle budget range of AMD's video products, judging by the previous generation's naming scheme). There's 128KB of L1 cache and 1MB of L2 cache available per core, and the APU supports dual-channel DDR3 memory at speeds of up to 1,866MHz. The A8-3870K of course also requires a motherboard that uses the (relatively) new FM1 socket, based on either AMD's A75 (with enhanced USB 3.0 and SATA III support) or A55 (USB 2.0 and SATA II) chipsets.

One important reminder about the graphics system on the APU: If you have a discrete video card installed, the APU will by default function as the boot-up video adapter, meaning any displays connected to a video card won't work until Windows loads the proper video drivers. This can be annoying if you only have one display, but you can toggle this "feature" in the motherboard's BIOS or UEFI settings. Second, the APU lets you access AMD's new Dual Graphics technology to "combine" the power of a discrete GPU with the integrated graphics; but this only works if both your hardware (the video card must be relatively low-end, and if you're only using one DIMM of memory, the whole thing might not work) and software (you'll need the AMD Vision Engine Control Center running) is correctly configured. Make sure your PC meets all the requirements before trying it out.

The biggest difference between the A8-3850 and the A8-3870K is in terms of the clocks. The CPU core on the newer chip has been bumped up from 2.9GHz to 3GHz, though the GPU clock remains unchanged at 600MHz?but both are now unlocked. This means you may overclock them to your heart's (and your PC's thermal) content, independently of each other, to get as much new performance as you can muster. It's also one of the first genuinely compelling reasons we've seen for enthusiasts (or just wannabes) to consider an APU that, by the broader standards of AMD's product line, is not an exceptional performer.

As we said when we reviewed the A8-3850 last year, Intel doesn't have any products that directly compare with AMD's new APUs in terms of overall capabilities. But if you care about raw processing more than graphics, an Intel platform based on chips like the lower-end Core i3-2100 or the considerably more powerful Core i5-2500K will serve you better. At its stock clock speeds, the A8-3870K represents only a tiny increase over the A8-3850; its multicore CineBench R11.5 score rose from 3.46 to 3.55, it took only six seconds less (5 minutes 12 seconds versus 5 minutes 18 seconds) to apply 12 filters in Adobe Photoshop CS5, cryptography throughput in TrueCrypt 7.0 raised from 106MBps to 109MBps, and its score in our full-system Futuremark PCMark 7 benchmark was functionally unchanged.

Video tests showed similarly small increases, with scores rising from 1,024 to 1,026 in 3DMark 11, frame rates increasing from 6.3 frames per second (fps) to 6.4fps in Lost Planet 2, and frame rates not improving at all in the Heaven Benchmark 2.5 (it remained at 5.5fps both times). These were all at basic resolutions, by the way?the Performance (1,280 by 720) preset for 3DMark 11, and 1,280 by 1,024 for the other two?though we maxed up all the details. By reducing the titles' resolutions or turning down the visual effects, you'll be able to get something much closer to playable frame rates, but you'll be making quite a few sacrifices.

This is where the overclocking comes in, right? Theoretically. We're happy to report that overclocking (when the APU was installed in the Gigabyte GA-A75-UD4H motherboard) was a breeze, and being able to separately focus on the CPU and GPU was an enormous frustration reducer. We had very little trouble nudging the GPU clock up from 600MHz to 900MHz and the CPU clock from 3GHz to 3.5GHz, using just a basic air cooler?and AMD tells us that, with more aggressive cooling and fine tuning of voltages, a combo rate of 960MHz/3.8GHz is possible. The A8-3870K offers you a lot of leeway.

But is it worth it? That depends on your point of view. The 3DMark 11 score rose from 1,026 to 1,244, CineBench from 0.90 to 1.04, the Heaven Benchmark from 5.5fps to 6.4fps, Lost Planet 2 from 6.4fps to 7.5fps, PCMark 11 from 2,509 to 2,691, Photoshop times down from 5:12 to 4:36, and TrueCrypt throughput up from 109MBps to 119MBps. (Predictably, load power rose as well, from 134.6 watts to 142.3 watts.) These aren't poor jumps by any stretch of the imagination. But except for those who might be really excited to overclock with such an inexpensive chip, we're not sure they're dazzling enough to set many hearts racing.

Still, the AMD A8-3870K is a fascinating part that shows how serious AMD continues to take the mainstream processor race. Our conclusion with this APU remains the same as with the A8-3850: Though you'll want a standalone video card for any real gaming purposes, AMD's blending of processing and video performance delivers a balance you just can't get from Intel right now. This may change when Intel ships its Ivy Bridge CPUs, which will support advanced DX11 graphics rather than Sandy Bridge's DX10, in a few months. But for now, AMD's Fusion approach is generating the most comforting heat in the midrange market.

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