Fusion is AMD's Atom Smasher

Alan Fackler

Nuclear fusion involves smashing small Atoms together to release incredible amounts of power. That’s likely what AMD hopes it can unleash when its next-generation Fusion APU’s hit the street early next year.

Dubbed Accelerated Processing Units, Fusion fuses one or two x86 cores with a fairly powerful graphics core in the hopes of smashing Intel’s popular but woefully underpowered Atom chips. And while it can’t take the mighty Nehalem microarchitecture chips head on in x86 performance, Fusion can definitely put a serious amount of pain on Intel’s Achilles’ heel : graphics performance.

AMD is doing away with its chip names in favor of case badges that hopefully help consumers make choices based on usage models.

Four chips will initially be offered in the first Fusion chip in the “Brazos” family in single or dual core configurations. Two “Zacate” chips and two “Ontario” chips. Different core clock speeds as well as GPU clocks will differentiate the chips as well as power consumption.

Fusion’s x86 is nothing too revolutionary from a pure x86 performance view. The company freely admits that the pair of x86 cores in Fusion are about 90 percent the performance of an original Athlon 64. In fact, in some compute-intensive cores, it may perform worse since the core has been tweaked from a 3-issue design to a 2-issue design. What that means in layman’s turns is that it’s a narrower core than Athlon 64. In comparison, one of the key performance advantages that Intel’s Core 2 had over Athlon 64 (among other’s) was its wider 4-issue core. AMD said it went with a narrower core  design to reduce power consumption.

The Zacate and Ontario versions of Fusion feature a K8 core that is tweaked to save power.  It's 2-issue instead of 3-issue, but AMD says an improved branch predictor and out of order engine will keep performance up.

The company said an improved branch predictor and “well managed” out of order engine helps keep the performance of the chip at better than Atom levels. And that is the point of the cores in the Fusion. They won’t set the world on fire but Fusion should out gun equivalent Atom parts.

But let’s be clear, Fusion is not about the x86 performance. It’s about graphics. That’s where AMD put the money shot in its first Fusion chip. With its third-generation unified video decoder core and support for H.264, DivX, Xvid, DX11 capability and 80 “nano-cores,” the first Fusion chips will have roughly the graphics performance of a Radeon HD 5450.

The memory controller in the platform is a single-channel memory controller capable of supporting 8GB of DDR3/1066 RAM.

That may not seem like much to a person used to Radeon HD 5970’s, but remember, we’re talking about a mobile chip that is incredibly tiny. The x86 cores and GPU along with the integrated memory controller, integrated PCI-E and other platform interfaces measures at roughly 75mm2 on TSMC’s 40nm process technology. Intel’s current D-series of Atom’s measure out at 87mm2 on the company’s 45nm process technology.

Two sets of PCI-E interfaces are available:  Four PCI-E 1.0 lanes off the APU and another four off of the Hudson southbridge.

Anyone who has ever used an Atom – even the current generation Atoms, can attest to the chip’s sluggish performance. And that’s at x86. Toggle over to anything graphics related on an Atom and the space time continuum will literally start running backwards because it’s that slow. To be fair to Atom, Intel’s graphics have always acted more like anti-accelerators. That’s not so with Fusion. We’re prohibited from disclosing raw numbers right now but we can say that it’s no Atom or even Arrandale in graphics performance. You can actually play some fairly modern games – if you’re open to dropping the resolution a bit.

We tested Zacate on a notebook test rig built by AMD for engineering purposes.

For example, we were able to play the hit game Call of Duty: Modern Warfare 2 at 1280x1024 resolution. Try to do that on a sub-$500 notebook with integrated graphics.

AMD’s messaging on power consumption is also a good one too. With the Zacate version of the chip, the company thinks worst case power consumption will be 18 watts. On the test platform we used, power draw for the complete computer at the socket was roughly 10 watts and under gaming loads 30 watts. The Ontario version which will target Atom’s will consume 9 watts. A typical Zacate-based notebook should run in excess of 7 hours and Ontario notebooks will push 10 hours.

The Zacate APU on the left, actually runs cooler than the Hudson southbridge shown on the right.

AMD said it was able to achieve that through clock and power gating and a C6 state to further reduce idle power. The first rev of Fusion, essentially, was not just a server or desktop chip chopped down to save power. AMD says it designed it from the get go to sip power.

So where will Fusion go head to head?

Even playing Call of Duty: Modern Warfare 2, Zacate runs cooler than a human.

AMD said Zacate or E-series chips will likely be used in $450 to $500 notebooks. The main competition will be Pentium-based notebooks with integrated graphics. Ontario or C-series chips will likely go into $300 or lower notebooks that compete squarely with Atom and Celeron notebooks with integrated graphics as well.

Based on a day of benchmarking a test rig outfitted with an E-350, we have to say that we’re suitably impressed. We certainly can’t render a verdict until we tested final product, but Zacate’s graphics performance could very well give it an edge over Intel’s current integrated graphics and possibly even against the upcoming Sandy Bridge chips.

The 40nm-based Zacate Fusion chip packs a dual x86 cores along with an 80 "nanocore" GPU and integrated memory controller and PCI-Express lanes.

As we said previously, we were able to play Call of Duty: Modern Warefare 2 at 1280x768 resolution (the likely res you’d play on a small wide-aspect ratio notebook). What’s the weakness: those x86 cores. Remember, you’re still talking about a slightly slower Athlon 64 dual core to push all of your applications that can’t leverage the graphics cores. While the Athlon 64 certainly slays an Atom, against a Penryn-based Celeron or Pentium or even a Westmere-based Core i3, it would likely get ugly.

But life is a compromise. And AMD believes that most people carrying $500 notebooks are more concerned with consuming video and games – not producing it. In other words, how many people do video encoding or editing on $300 Netbooks or sit down to crunch a massive spreadsheet with a cheap notebook? Probably not many.

All the chips in the Brazos family of Fusion will be ball grid array only to save space.  AMD says motherboard makers plan to sell boards with the chip already installed soldered in place.

Overall, I’m pretty excited by Fusion. To be able to get discrete-level performance in a sub $500 notebook (and sub $300 netbook) is pretty revolutionary. Fusion isn’t just about netbooks either. I’m looking forward to a HTPC that sips 10 watts but can accelerate higher definition content. And once we see Fusion APU’s combining AMD’s next-generation Bulldozer core in 2012, we will truly be in a brave new world.

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