Graphics: Fewer Shaders, Better Efficiency
As Don pointed out in his mobile A10-4600M coverage, shifting Trinity to the VLIW4 architecture first found in AMD’s Radeon HD 6900-series cards allows it to deploy fewer shaders, but take better advantage of them. By then turning clock rate up or down (depending on thermal headroom), it’s able to improve performance without adding a lot of complexity to the APU itself.
At its most feature-complete, Trinity’s Devastator graphics processor includes as many as six SIMD engines, each with four texture units and 16 thread processors. There are four ALUs in each thread processor, adding up to 384 total shaders and 24 texture units.
Sliding down AMD’s stack, SIMD engines are gradually turned off and clock rates are dialed down to create differentiation. The A10s both have 384 shaders. The A8s lose two SIMDs (and eight texture units), creating a 256-shader component. AMD’s A6-5400K sports three SIMDs, totaling 192 shaders. And the A4 looks to be a 128-shader offering.
Like Llano, Trinity supports Dual Graphics configurations—cooperative rendering using the on-die Radeon engine and a discrete card of roughly comparable potency. Although I don’t have any of the models AMD lists in its support matrix, I did discover that a Radeon HD 6670 does the trick as well.
Our baseline blue bars represent the Radeon HD 7660D built into the A10-5800K APU. The green bars are our Radeon HD 6670 on its own. And the red bar is both graphics engines working cooperatively.
At 1280x720 there isn’t enough graphics load to let Dual Graphics shine before this platform runs into a processor bottleneck. The gap opens up at 1680x1050, though, and continues to show off the benefit of Dual Graphics at 1920x1080, where the integrated Radeon HD 7660D and Radeon HD 6670 average almost 100 FPS.
|Discrete GPU||Desktop APU|
|Discrete Graphics Code-Name||Radeon Product Name||Recommended Memory||A6-SeriesHD 7540D||A8-SeriesHD 7560D||A10-SeriesHD 7660D|
|Turks XT||HD 7670||GDDR5||Discrete Available||Discrete Recommended||Discrete Recommended|
|Turks Pro||HD 7570||GDDR5||Discrete Available||Discrete Recommended||Discrete Recommended|
|Turks Pro||HD 7570||DDR3||Discrete Recommended||Discrete Recommended||Discrete Recommended|
|Caicos XT||HD 7470||DDR3||Discrete Recommended||Discrete Available||Discrete Available|
|Caicos Pro||HD 7450||DDR3||Discrete Available||No Discrete (APU-Only)||No Discrete (APU-Only)|
|Onega LP||HD 7670A||GDDR5||Discrete Recommended||Discrete Recommended||Discrete Recommended|
|Onega LP||HD 7650A||DDR3||Discrete Recommended||Discrete Recommended||Discrete Recommended|
|Caspian XT||HD 7470A||DDR3||Discrete Recommended||Discrete Available||Discrete Available|
|Caspian Pro||HD 7450A||DDR3||Discrete Available||No Discrete (APU-Only)||No Discrete (APU-Only)|
|Cedar||HD 7350A||DDR3||No Discrete (APU-Only)||No Discrete (APU-Only)||No Discrete (APU-Only)|
We also benchmarked Batman: Arkham City using the Low quality setting preset and found that performance actually slid backward with Dual Graphics enabled. The version of the driver we tested, however, still doesn't offer Dual Graphics support in anything but DirectX 11 applications. You don't get DX 11 features in Batman until you choose a higher preset. Fortunately, AMD has a beta driver (Catalyst 12.6) that adds DirectX 9 compatibility, too. We didn't have time to give it a spin before today's piece, but it's something we'll follow-up on.
What we do know from WoW is that Dual Graphics has serious potential on this platform. Notably, the setup process is significantly easier than it was back when I evaluated Llano. You simply plug in the discrete card, keep your display attached to the on-board GPU, and install the drivers. Dual Graphics even gets enabled automatically now.
Another advantage that Trinity holds over Llano is Eyefinity support. The new APU includes four display controllers, whereas its predecessor only included two. That means you can do three- or four-way monitor configurations, providing you use the right combination of outputs. Four screens, for example, require DisplayPort 1.2 multi-streaming on at least one output. A trio of screens is easier. You can use two non-DisplayPort panels, plus one DisplayPort- or VGA-equipped screen as the third.