The past few years haven’t been kind to AMD, with everything from a mass exodus of staff to the poor performance of its ‘Bulldozer’ cored desktop CPU hitting the company hard. But the bright spot in all of this has been its APU strategy, the ultimate fruit of the union between it and ATI. Last year AMD not only managed to make Intel’s Atom irrelevant with its E-series APUs but it delivered a highly compelling mainstream laptop processor in the form of the Llano series of APUs.
AMD’s market is still a fraction of Intel’s, but thanks to these APUs it actually grew last year. Now it is time for the second generation of laptop APUs, based upon the new ‘Trinity’ core design. This new design consists of a tweaked up version of the Bulldozer CPU core, codenamed Piledriver, and pairs it with a GPU based on AMD’s older ‘Northern Islands’ architecture.
Bulldozer got off to a bad start last year when it launched as the FX-8150 desktop CPU. AMD has made some bold decisions with its architecture, implementing what amounts to a hardware version of hyper threading consisting of modules. In this design a module has two CPU ‘cores’ – each of which has its own integer unit but shares a floating point unit with its partner.
While this seems a logical approach in a world where multiple CPU cores are still rarely used to their maximum ability, it emerged that Windows couldn’t distinguish between cores and modules, which meant its scheduler didn’t use the CPU to its maximum potential. Rather than the ideal situation, which would prioritise one core on each module, Windows just addressed cores as they appeared, which meant some modules would be working overtime while others sat idle.
Add to this the fact that Bulldozer performance would never have been equal to Intel’s current CPU performance, and AMD is well behind on CPU performance. It becomes incredibly difficult to recommend most of AMD’s FX lineup because of this, but that doesn’t mean that Trinity is doomed to fail.
This is because APUs are about more than just CPU performance, especially in laptops. They are about delivering the kind of day in, day out performance required from portable computing, and doing so with a processor that can handle everything thrown at it.
For while AMD’s raw CPU performance lags behind Intel’s, its GPU performance is world class. Graphics performance was the standout aspect of Llano, and with Trinity it has been further improved. AMD is using the Northern Islands GPU design seen on the Radeon HD 6950 and 6970, rather than the newer Southern Islands architecture used for the 7970 and 7950, but to the end user this doesn’t really matter.
What does matter is the improvements made to the way the GPU works in Trinity. While it technically has less stream processors than Llano did, they are more efficient thanks to the VLIW4 design of the North Islands GPU. AMD has also improved tessellation performance with Trinity. This means overall faster GPU performance than llano, which is enhanced thanks to the introduction of Turbo across both the CPU and GPU. This means that when the CPU is under a relatively light load the GPU can use the excess TDP to push itself faster – in Llano dynamic Turbo only worked on the CPU cores and left the GPU alone.
AMD has kept the UVD3 video decoding hardware seen in Trinity, which was one of our favourite parts of the APU. By using a hardware video decoding block, combined with aggressive power gating, AMD can effectively shut down most of the APU while playing back video. This means that watching stuff on an APU based laptop results in much lower power draw than if the CPU or GPU was doing the decoding (while also allowing the GPU to run post processing on the decoded video if needed). With Trinity AMD has added a video encoding engine as well, taken from the GCN architecture used for the 7970 and 7950. This brings similar speed and power consumption advantages to the process of encoding video, given software that supports the technology.
Just looking at the architectural changes is enough to give us a good mental picture of where Trinity will sit in the performance curve. Lower CPU but better GPU performance than the equivalent Intel chips is a given, as is excellent battery life. Our benchmarks confirm these expectations quite nicely.
Our testing has been done with AMD’s reference platform for Trinity. This is an unbranded laptop featuring an A10-4600M APU, 4GB memory, 128GB SSD and a 1366 x 768 screen. The A10-4600M has a TDP of 35W, making it a higher end laptop part, and runs at a standard frequency of 2.3GHz.
For comparison we also tested one of Intel’s new 45W Ivy Bridge models, the Core i7-3720QM. This uses the latest Ivy Bridge core and while not a direct competitor to the A10, it does give a good idea of how the two architectures compare.
Let us get the bad part out of the way first – AMD’s CPU performance is perfectly acceptable for day to day tasks but nothing outstanding. In our real world benchmarks it scores an overall 0.57, an incremental improvement over the score of 0.51 from the previous generation Llano based A8-3500M but significantly down on the score of 1 delivered by the 3720QM. Looking through previous reviews, the Trinity score is about what we’d expect from a Sandy Bridge based Core-i5 2467M Ultrabook processor from Intel, which offers good-enough CPU performance for most day to day tasks.
Trinity starts to look a lot more tempting when you look at the other parts of the puzzle. In our battery life tests we saw the reference laptop hitting seven hours under light load and just under two hours under heavy load. This is slightly less light use staying power than the reference system for Llano was capable of, but significantly more than what we managed to get out of the Core i7-3720QM reference system (which managed to last 3 hours and 35 minutes under light load). Ultimately the amount of life that you can squeeze out of your laptop comes down to individual product design, so while AMD’s reference platform bodes well, we will need to wait for production laptops before we get a good handle on real world battery life.
Where AMD’s new platform does shine brightly is in the graphics department. Despite the vast improvements seen with Intel’s processor graphics in recent generations, AMD still has the upper hand in performance thanks to its Radeon GPUs. In our Crysis benchmark we managed to eke 49fps out of the GPU in low detail, at 1366 x 768, and a marginally playable 26fps at medium detail. This is a slight gain over Llano, and a touch more than what we saw from the top of the range implementation of Ivy bridge, which scored 46 and 24fps. It coped wonderfully with game of the moment Diablo 3, delivering 50fps with most settings cranked to medium or high.
While the gap has narrowed, the A10 APU is a much cheaper offering than the Core i7-3720QM (which costs roughly $600 for the CPU alone), and is targeted more at the midrange and Ultrabook processors that Intel has yet to unveil. Unfortunately we also haven’t been able to test how AMD’s dual graphics technology works with Trinity, as the test laptop lacks the discreet AMD GPU needed to get the technology running.
Ultimately what makes or breaks Trinity is going to be price. As long as Trinity-based laptops are less expensive than the Intel equivalent, then the overall experience is quite compelling. However we are on the cusp of a flood of new Ivy Bridge laptops, and a lot of these will ship with discrete GPUs that will deliver more performance than either Intel or AMD can deliver. This will be especially important when we start looking at lower wattage Trinity APUs, designed to appear in designs similar to those used by Ultrabooks. If AMD can maintain great GPU performance in that space, then it has a very compelling offering on its hands. In many ways this means that we are now awaiting the arrival of actual Trinity-based laptops to see just how well they perform in the real world.
