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AMD's A10-7800 processor reviewed

..and the A6-7400K, too

We first reviewed an AMD Kaveri processor back at the start of the year, but since then, AMD's new APU has been in kind of a weird place. The A8-7600 chip we reviewed has been scarce in retail channels, evidently because AMD succeeded in selling them elsewhere—likely to big PC manufacturers. Some of the chips were surely set aside for use in laptops, too. As a result, PC hobbyists just haven't had very good access to AMD's latest APU.

Happily, that situation is finally changing, and Kaveri-based chips are starting to make their way into the market. AMD is putting an exclamation point on that fact today by filling out its APU lineup and making some tweaks to its pricing. The headliner of the bunch is a brand-new model, the A10-7800, that may just be the most desirable Kaveri-based desktop processor yet.

Kaveri proliferates
Here's a look at AMD's updated lineup:

Model Base
L2 cache
A10-7850K 3.7 4.0 2/4 4 8 720 95 - $173
A10-7800 3.5 3.9 2/4 4 8 720 65 45 $155
A10-7700K 3.4 3.8 2/4 4 6 720 95 - $155
A8-7600 3.3 3.8 2/4 4 6 720 65 45 $105
A6-7400K 3.5 3.9 1/2 1 4 756 65 45 $77

The brand-spanking-new A10-7800 nearly matches the top-of-the-line A10-7850K in terms of clock speeds and unit counts, but it does so in a much smaller 65W power envelope. And it costs less than the 7850K. Given everything, I'd say the A10-7800 is the Kaveri chip to get, as long as you don't plan on overclocking your processor. (Only the K-series parts have unlocked multipliers.)

Also new today are official retail editions of the A8-7600 and A6-7400K. The A8-7600 is the same basic product we reviewed in January, while the A6-7400K is an unlocked K-series part. At $77, the 7400K matches up against the unlocked Pentium G3258, but going directly against an overclocking titan like that one would probably be suicidal. The 7400K is better suited to providing an attractive CPU-IGP combo for truly low-end systems.

At $155, the A10-7800 is priced in a gap between Intel's Core i3 and i5 desktop parts. That's a clever tactical move by AMD. The company's marketing materials clearly position the A10 against the Core i5, so the firm is looking to be the lower-cost alternative. As we'll see, though, the A10-7800 will have to deal with some of the top Core i3 offerings in order to stake that claim.

Meanwhile, the new Kaveri-based APUs face some unusally formidable competition from a familar source: past generations of AMD APUs, specifically those based on 32-nm Richland chips.

As we noted in our initial review, AMD had some tough choices to make with Kaveri. The 28-nm process provided by its chipmaking partner, GlobalFoundries, offers some potential advantages, including increased power efficiency and the ability to pack more logic into a given area. AMD has used the extra gates to cram in lots of graphics horsepower—specifically in the form of the GCN graphics architecture used in the latest Radeons. GlobalFoundries' 28-nm process is not, however, tailor-made for CPUs like its older 32-nm SOI process was. The transistors in Kaveri chips can't switch quite as quickly as those in AMD's 32-nm chips, and as a result, CPU clock speeds are somewhat lower.

For instance, the A10-7800 ostensibly replaces the Richland-based A10-6700. Both are 65W quad-core processors. The A10-6700 has a base clock of 3.7GHz and a Turbo peak of 4.3GHz. By contrast, the A10-7800 runs at 3.5/3.7GHz.

AMD has attempted to make up this deficit by tweaking the "Steamroller" CPU cores in Kaveri to increase per-clock instruction throughput. As we'll soon see, those improvements have paid off to some degree. Still, this isn't the best time for AMD to be treading water when it comes to CPU performance, given how big a lead Intel holds in this department.

AMD hopes to paper over its relative weakness in CPU performance by pushing for more desktop applications to use the GPU side of the chip to help with computing tasks. The concept makes sense—and heck, tablets and phones are using GPU acceleration pretty consistently these days—but unfortunately, Windows applications that take advantage of GPU computing have been slow in coming. Speaking of which...

What about that 12-core APU?
No, Virginia, AMD is not releasing a 12-core processor any time soon.

The Internets have been afire with a rumor about a 12-core APU lately, prompted by some AMD marketing materials that focus on the number 12.

I suppose the enthusiasm is natural; 12 cores is a lot of cores. I'm not sure what folks expect to do with them all, but whatever. Here's the thing, though: in its push for "converged" computing, AMD has taken to calling its graphics compute units "cores." By this reckoning, the A10-7800, with four CPU cores and eight graphics "cores," would be a 12-core processor.

So I guess AMD really is introducing a 12-core processor. They've also had another one on the market for a while now.

Mind blown. Poof.

Meanwhile, Intel sells a Core i5 chip with four CPU cores and 20 graphics execution units, so it has 24 cores, right?

Hrm. I'm not so sure about this new math.