Power concerns, summary
Dual Graphics, aka CrossFire, scale nicely in 3DMark 11, providing a 35 per cent uplift over just running the Radeon HD 6670 on either platform.
More of the same in 3DMark Vantage, where we see a 20 per cent-plus improvement.
Getting an award for stating the bloomin' obvious, adding a discrete card to an APU-only system increases overall power consumption. The trio of systems housing said card consume around 10W more when idling.
Here's a telling graph. Stick the HD 6670 into the Intel PC and it still draws less juice, as a platform, than the A10-5800K alone. Including the discrete card pushes power consumption up to 140W, or 40 per cent more than the Intel rig.
Dual Graphics is a feature of AMD Trinity APU systems that enables users to add a circa -£50 discrete Radeon graphics card - HD 6600-series, preferably - and lash it alongside the similar HD 7660D graphics built into the chip. Going down this route facilitates CrossFire multi-GPU rendering, useful for potentially increasing gaming performance without any further financial outlay. It's important to understand this feature is not available if choosing a price-comparable Intel platform.
The usefulness of Dual Graphics as a means of providing more gaming performance is wholly dependent on how well the title scales through CrossFire software technology. The best-case scenarios, such as DiRT Showdown, show a 40 per cent frame-rate increase over using the discrete card alone, as you would do if installing it on, say, an Intel Core i3 machine. On the flipside, Batman: Arkham City is indifferent to the charms of Dual Graphics, to the extent that performance actually drops off.
Our examination also finds that an Intel Core i3-3225 platform performs a smidge better than an AMD A10-5800K when evaluated with a discrete HD 6670 in the PCIe slot. What's more, the Core i3's power consumption is better than AMD's. Swings and roundabouts, eh?
We believe that an AMD APU's Dual Graphics capability is a useful feature if you happen to have an add-in card that closely resembles the on-board graphics' architecture. There's a reasonable chance of gaining extra performance, as shown by our benchmarks, at no extra cost. Dual Graphics, then, makes most sense in fixed-specification A10-5800K-powered base units that ship with the necessary HD 6600-series supporting cards.
Readers who consider themselves proper gamers would still be best-advised at spending at least an APU-matching £100 on a mid-range graphics card, because a Radeon HD 7850 or GeForce GTX 660 assuredly knock the spots off anything a well-matched Dual Graphics configuration can offer.