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AMD's A8-3800 Fusion APU


Llano slides into a smaller power envelope
— 10:28 PM on October 2, 2011

When they first hit the scene this summer, we thought AMD's new A-series APUs—more commonly referred to in certain circles by their code-name, Llano—were a nice fit for laptops. Llano silicon combines four relatively low-speed CPU cores with an integrated Radeon graphics processor, and AMD focused lots of attention on making sure the chip only sips power at idle, to prolong battery life. Intel's competing Core i3 processors have two fast cores, and Llano's quad cores give it nearly comparable CPU performance, while its Radeon IGP runs circles around Intel's rather anemic graphics. In all, the mobile A-series APUs are an attractive alternative to the latest from the Intel juggernaut—no minor achievement these days.

When AMD attempted to migrate Llano's competitive formula onto the desktop, though, the road got bumpy. The CPU cores needed a big clock frequency boost in order to compete with Intel's desktop Core i3 processors, and to get there, AMD had to raise the chip's operating voltage substantially. As a result, the first desktop Llano, the A8-3850 APU, had an outsized power envelope of 100W—5W higher than the Phenom II X4 840 it ostensibly replaced (which was made on an old 45-nm fabrication process) and worlds apart from the competition, the 65W Core i3-2100. Worse, the A8-3850's four CPU cores were still notably slower than the Core i3's dual cores, especially in single-threaded applications.

Llano retained its advantage in graphics horsepower over the Intel IGP, but we had trouble seeing the value proposition of a 100W chip whose primary attraction was somewhat nicer integrated graphics than the 65W competition—especially when a cheap video card would provide better graphics than any IGP. In short, Llano wasn't terribly attractive when it moved too far from its original mission as a low-power solution for highly integrated systems like laptops. Fortunately, AMD also promised to release 65W versions of Llano for the desktop eventually, and we looked forward to those as a potentially smarter choice with more of a natural fit in some parts of the market.


The A8-3800 APU

Although they are currently in short supply due to manufacturing problems, the 65W desktop variants of Llano have intermittently popped up in stock at various online retailers in recent weeks. They are out there, even if they're a little scarce right now—and fortunately, we've gotten our hands on one of 'em, the A8-3800 APU.


The A8-3800 differs from the A8-3850 we've already reviewed in just a few respects, the most obvious being its 65W thermal design power (TDP) rating. Also unlike the A8-3850, the A8-3800 makes use of AMD's Turbo Core dynamic clock frequency tech, which allows the chip to range up to higher clock speeds temporarily when there's thermal headroom available—that is, when not all of the CPU cores are heavily burdened at once. In this case, the A8-3800 can stray from its 2.4GHz base clock up to 2.7GHz. Those frequencies leave the A8-3800 a bit behind the A8-3850, whose four cores regularly run at 2.9GHz. Happily, though, AMD didn't have to compromise on the 3800's graphics in order to fit into the smaller power envelope. The two products share the same Radeon HD 6550D IGP with 400 shader ALUs at 600MHz.


A look at the underside of the A8-3800 and the Socket FM1 mechanism that holds it

The A8-3800's list price is $129, ten bucks less than the A8-3850's. That means its primary competition from Intel is similar: the Core i3-2100 at $117, or perhaps more appropriately, the Core i3-2105 at $134. The difference between those two Core i3 models is simple: the i3-2105 has full-on Intel HD 3000 graphics, not the chopped-in-half HD 2000 variant in the i3-2100. Their CPU performance should be the same. Thus, we've tested both chips, but we've confined the Core i3-2105 to our integrated graphics tests alone.

As if the competiton weren't formidable enough, Intel has recently released a few new models, some at overlapping prices. For instance, the Core i3-2125 lists for $134, runs at 3.3GHz (200MHz faster than the i3-2105), and also has an HD 3000 IGP. The Core i3-2130 runs at 3.4GHz and sells for $138, but has HD 2000 graphics. We haven't tested them yet, but the slight CPU clock speed boosts should make these newer models even tougher competition for the A8-3800. Still, they're not likely to alter any key dynamics fundamentally, as you'll understand once we get into the performance results.

Oh, and the results on the following pages were obtained with the same configurations detailed on this page of our A8-3850 review. We've just dropped the A8-3800 into our Llano test rig and added it to the mix.