AMD has a long and proud history of developing great mobile GPUs, but it hasn’t been able to replicate the success with CPUs. Intel has historically won on performance and battery life, and with Sandy Bridge it has integrated graphics that no longer suck for gaming. Unfortunately it looks like the minor victory with Sandy Bridge graphics will be short lived for Intel, because AMD has just launched its llano APU for notebooks and in the process has raised the bar for gaming.
Key to this performance is the way in which AMD has combined a four core Phenom CPU and 400 Stream processor RADEON GPU onto the same piece of silicon. It is a fascinating piece of architecture, and while we always knew the promise of Fusion it is fantastic to see just how AMD has implemented its llano design.
Integrated graphics are not a new thing. But historically integrated graphics are designed to do the bare minimum – they can display a windows desktop, play back video and run games at a very rudimentary level. When Intel moved its integrated graphics into the CPU with Sandy Bridge we were quite impressed, as it finally brought acceptable DirectX 9 gaming performance to the integrated space.
What AMD has done with Llano is something else entirely. Rather than integrated graphics AMD claims it has an integrated GPU, promising the sort of performance normally seen only with discreet graphics cards. One only has to take a look at the die shot for llano in order to see just how much space is given over to graphics, in Sandy Bridge the graphics engine occupies a fraction of the space at the side of the die, whereas nearly half of llano is given over to graphics processing.
In essence the llano die is broken into five main parts. It has up to four CPU cores, based on the same ‘Stars’ design as the current range of Phenom processors. Each of these CPU cores has a dedicated 1MB of L2 cache (in contrast to Sandy Bridge where cache is shared across cores) and improved prefetch. This translates to the cores being slightly higher performers than the Phenom, but only in the realm of 6% faster.
Alongside these CPU cores sits the GPU portion of the processor. This consists of 400 stream processors that are capable of supporting DirectX 11. Next to the GPU sits AMD’s third generation Universal Video Decoder (UVD3), which is capable of hardware decoding of common video formats like Xvid and DivX. The APU also has an ‘integrated Northbridge’ designed to control things like PCI-Express and memory access as well as a DDR3 memory controller and display controllers built in.
The llano die gives a lot of space over to the GPU
What this all means is that AMD is able to turn off large chunks of the APU when not in use. By including a hardware video decoder, for example, it can power down the CPU cores when you watch a movie, saving on unnecessary power. It also means that the GPU part of the processor can be used to improve image quality rather than be used for raw decoding of video.
While it looks like AMD has just bolted a CPU and GPU together, the actuality of the APU design is much more complex. It has had to account for the fact that discreet GPUs traditionally have massive memory bandwidth (which is tightly tied to performance), while CPUs are used to flooding system memory with calls. This means that the GPU on llano can talk directly to the memory, rather than having to go via the CPU, which in turn makes for much better performance.
Technically llano is a massively impressive achievement, but that all means very little if the real world performance doesn’t reflect this. But before we dive into the performance of the APU, there are a few things to keep in mind.
Without even running a benchmark we can state that raw CPU performance will be lower on the APU than an equivalent Sandy Bridge CPU. But in reality this isn’t as much of an issue as it would have been a decade ago, because we can also say that AMD’s graphics performance will outdo Intel’s. A few years ago this would have just meant that the APU is a better gaming chip, which it is, but the rise of GPU accelerated applications invalidates a lot of preconceptions about this.
Duke Nukem Forever on a Fusion APU. Some said this day would never come.
But fire up our A8-3500M review laptop and install a game and prepare to be blown away. Dirt 3 runs at 35fps in medium detail just on the integrated graphics, jumping up to 65fps when we enable ‘Dual Graphics’. Dual Graphics is the term AMD is giving to one of its secret weapons, an asynchronous implementation of crossfire that allows laptops with Discreet GPUs to get a performance boost from the APU. Unlike the alternate frame rendering of desktop crossfire this implementation renders one frame on the APU for every three on the GPU, but it still ends up delivering more performance than using either in isolation.
What impressed us even more was testing with Shogun: Total War 2. We are intimately aware of how hungry the game can be, so when we ran the DX11 720p balanced settings benchmark (using Dual Graphics) we were astonished. A solid 35fps were averaged, which is more than ample to play the recent strategy game. Curiously when we cranked the settings back to DX9 the result was a full ten frames slower, highlighting the importance of DirectX 11 support for performance.
Every other game that we have thrown at our review sample has been playable. Because the APU is ultimately limited by memory bandwidth you’ll likely need to spend some time tweaking graphics settings to make the most out of it, but the overall gaming experience is far superior to anything that we have seen on a mainstream laptop. AMD is aiming the A series directly at Core i5 and i3 laptops, so expect to see similar price points.
Once we have our hands on some retail models we’ll look more closely at gaming over the variety of AMD A series APUs, and in a month or so we’ll talk desktop versions. But for now rest assured that AMD has delivered on its Fusion promises yet again, and while we will have to wait for its next high end move with the ‘Zambezi’ cored FX processors, those after an affordable gaming laptop are being well served.
John Gillooly travelled to Abu Dhabi as a guest of AMD for the Llano Tech Day briefings.