AMD Dual Graphics Performance and Scaling
AMD’s Dual Graphics is a new name for a technology that has been around or discussed almost as long as the recent rejuvenation of multi-GPU graphics. The idea of "Hybrid SLI" or "Hybrid CrossFire" was always the combination of a discrete GPU and integrated graphics though at that time the integrated graphics was on a chipset. Both AMD and NVIDIA shipped products with this for quite some time although the uptake for it was never that substantial. The reasons seemed simple enough: those who were interested enough in gaming to know what CrossFire or SLI was weren’t the same people buying integrated graphics based computers for gaming.
Dual Graphics is a rebrand that attempts to pair the AMD Llano based integrated graphics with certain discrete GPUs. The list is limited so don’t plan on taking that spare Radeon HD 5830 you have sitting around and getting a boost on it. Here is the list:
The four discrete graphics cards currently supported are the Radeon HD 6670, HD 6570, HD 6450 and the HD 6350. You can see in the above table that when combined with either the A8 or A6-based APU, the combination is actually assigned a new model number as well. In our testing we used the A8-3850 and the HD 6670 which will be rebranded as the Radeon HD 6690D2. The D2 indicates that we are using a Dual Graphics implementation here. This mostly for system builders and retail differentiation – we just need to know that the combination of the HD 6670 and the HD 6550D integrated graphics is supposed to be faster than each individually.
I should note here that there is another requirement that wasn’t blatantly obvious to me before starting testing: AMD says that Dual Graphics technology, which is enabled by simply hitting the "Enable CrossFire" button in the new AMD control panel, will only work on DX10 and DX11 games, NOT on DX9 titles. I have two problems with this. First, this goes against all we know about multi-GPU technology up until today – we have never had to differentiate between DirectX versions before. Maybe budget gamers won’t have that stigma, sure, I get it. But my second issue is that many games, including current ones like Dirt 2 and Shogun 2, actually use DX9 code paths at lower image quality settings. And since we are talking about budget to *maybe* mainstream performance level graphics, I would bet that these games will be run at those lower settings anyway. So until the DX11 conversion for games is complete (which is likely years away) Dual Graphics won’t be fully utilized.
So, what does our testing look like then?
So only 3DMark Vantage (which is DX10) and Dirt 3 (which is DX10/11) saw performance gains going from just the Radeon HD 6670 to the Dual Graphics configuration. The other titles, Left 4 Dead 2, Civilization V (which crashed consistently when Dual Graphics enabled) and StarCraft II saw no gains at all.
Obviously if you limit the testing to games that are DX10/11 only then you will see some performance boosts here and it is also likely that had we used the HD 6570 instead of the HD 6670, the performance boost from the Dual Graphics technology would have been more substantial. As it is, the HD 6670 is so much more powerful than the HD 6550D graphics in Llano that seeing the 11% boost in Dirt 3 at 1680×1050 is actually pretty good.
We plan on taking some more time with Dual Graphics in July to see if we can’t iron out some of these issues and get some more information on the DX9 vs DX10/11 issue and report back. For now I would consider this feature a minor advantage at most for Llano.