AMD Fusion APU explained

Zacate mobile processor has a new core and a new acronym

AMD Fusion APU explained

Zacate is a Spanish noun that means grasses, generally those used for grazing animals. It is used chiefly in Mexico. It's also the code name for AMD's new wunderkind.

This Zacate is a little low-power number aimed at notebooks, and is more than a straight Intel Atom rival, it's a bit beefier than that. Zacate is the first of AMD's two new cores and reflects its new design philosophy; and shows the direction AMD is going, so take note.

Zacate is a twin-core chip (well, one version is), and these cores are the completely new Bobcat design. Sitting next to these on the die are integrated graphics. Zacate is the first of what AMD has dubbed Fusion APUs.

APU (Accelerated Processor Unit) is AMD's term for bunging graphics onto the die and Fusion is AMD's name for its new approach at doing this. Fusion is the coming together of processor and graphics in a single chip in co-operative manner, hence the name 'fusion' [I think everyone gets it now, move on – Ed].

Integrated and okay?

The basic block diagram of a Fusion APU puts a graphics engine on one side, a processor, or processors, on the other and between them a bus and memory controller. Both sides share the system resources depending on the job in hand.

Test rig 2

Instead of thinking of two discrete data processors doing two jobs, we have a single unit programmed as one, with operations piped down the most suitable route. GPUs are only specialised CPUs after all.

It was the Fusion programme that drove AMD to buy ATI in 2006, as it needed the company's GPU expertise. PCs boasting integrated graphics have only really been tolerable in laptops out of necessity. Any desktop listing such a feature is rightly shunned by any right-thinking person. Fusion should bring us on-board graphics that we might actually be pleased about.

Okay, that might be going a bit far, we may not run away in horror though. The concept is due to creep up the form factors, from netbooks and thin laptops through to mini-PCs and onwards.

Refreshing re-think

The blurb from AMD talks big. Fusion is "a new approach to processor design", and is "ushering in a new era of visual computing experiences". It takes on an epic biblical air in places, but all cynicism aside, Fusion is a refreshing re-think, especially if the SDKs get a good airing and code is written with them in mind.

The aim is a decent graphical punch in a small system – what's not to like? Along with the nice new Bobcat cores the new GPU is DX11 capable and has 80 stream processors. If this were a new desktop graphics card we might pause and cogitate here as that's not a lot of stream processors, but putting it into context of a tiny low-power chip that's not half bad.

Do you want high definition video? Of course you do and there is a unified video decoder specifically for the job.

Zacate's processor cores and GPU are clocked differently, the later being a fair bit slower (current estimates reckon on 500MHz maximum). The whole package comes in with a TDP of 18W. Low, but not ultra low enough for really small packages where Atom has been pitching its tent.

Zacate comes on a tiny 40nm die and is a BGA package (that means soldered directly on to boards). Memory consists of a single channel of DDR3-1333.

There will be two initial flavours: the twin core E350 and the single core E240, which will be the same, but one core is zapped.

To go with the new chip, we have a new hub chip, the Hudson DI. This connects to Zacate via a PCI-e 2.0 x4 bus (fast enough for now). Hudson will carry SATA 300 and USB 2.0, but no Ethernet (huh?).

First public run

At the unveiling of Zacate (held at the same time as Intel's IDF – just for kicks) AMD pitted a Zacate development rig against a mainstream laptop running an Intel i5 520, which also boasted integrated graphics, of course.

test rig 1

Running City of Heroes at 1,024 x 769 pixels, the Intel-powered notebook managed around 16 to 17fps. The Zacate board trotted along at a more acceptable 30fps. That's nearly twice as fast, folks.

Some questions were raised about drivers and whether or not it was a level playing field, but honestly can't you lot be impressed for a change? No, suspect everyone, it's the only way to be sure.

Some fiddling about with drivers and the use of other games and benchmarks followed. It transpires that while some results are only on a par with the 520 (the IE9 benchmark is as near as makes no odds), it is still a highly impressive games chip.

Reportedly Batman Arkham Asylum ran at 16.5 fps as against 11.3fps and City of Heroes 39.6fps against 25.5fps. That's still half as fast again – tasty.

The killer is that Zacate is doing this with a TDP of 18W, while the Intel i5 520 takes a more substantial 35W, which translates into mucho battery life. This means they won't be direct rivals as such, which is all the more impressive.

All in all, Zacate looks to be a very good thing. Obviously AMD has spent a small fortune developing it and so it jolly well better had be. What we will get is faster portables with better gaming – no complaints there.

Does this mean we can live in a world where real high-power gaming is properly portable and we can finally do what we always dreamed of? Playing proper butt-clenching 3D games while sat anywhere we like. No. Desktops will remain gaming kings and always will. There is just no getting around the fact that your desktop PC can put 300W through a graphics card.

Are we nearly there yet?

We should see Zacate-powered hardware early next year. Initially, it'll be machines in the lower half of the portable market. Mini-ATX boards will follow, so we can expect other formats. There are Atom-powered servers around, so perhaps we will see Zacate or something very similar.

Bang per watt is attractive in all form factors. What have we missed? Oh yeah, clock speeds. Nothing official on this at the time of writing, although 1.6GHz has been touted. The days when it was all about frequencies are over (unless it makes you look especially good, of course).

Also, don't expect to see the names Zacate and Bobcat splashed about when the hardware arrives. These are just code names and branding will be under a different banner.

AMD has the Vision brand all ready and waiting as well as the Fusion name. The world of netbooks and laptops is going to get a lot more competitive and capable. Zacate is just AMD's vanguard too, there's a lot more to come.

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