Where does this leave you?
So what have we learnt by looking at two GeForce GTX 670 cards tied together in SLI? Our testing show that, even with super-high-end in-game settings, they're overkill when running a single monitor with a now-ubiquitous 1,920x1,080 resolution. One really needs to invest in either a 3D panel or run three panels in Surround model to make the most use out of them.
Run with three side-by-side screens and performance at the lofty 5,760x1,080 resolution is very solid, beating out a single card by up to 90 per cent. Efficient GPU Boosting capabilities translate to overall gameplay that's almost on a par with the ultimate graphics card, the GeForce GTX 690. The intrinsic beauty of a two-card graphics subsystem based inside an SLI-capable system is that you can buy one now and, should the need arise and funds are sufficient, upgrade to another when in due course.
But examination of the average and per-second framerate sometimes doesn't reveal all. A closer look at per-frame performance shows there are instances where the frame-latency output from a twin-GPU setup is less than optimal. This up-and-down behaviour affects all cards - single- or dual-GPU - to some degree but is more prevalent when running two boards. In most real-world cases the in-game slowdown isn't as noticeable as the numbers may suggest, though it is worth understanding this micro-level behaviour before committing funds for an expensive purchase.
The talk about frame-latency issues is an interesting topic that deserves an article of its own. This particular one is more concerned with the comparative value offered by two GeForce GTX 670s in SLI. Looking at the numbers produced from one GTX 670 and GTX 690, the £650 GTX 670 SLI fits in nicely and makes a viable case to be included in an ultra-enthusiast's system.
What do you think? Do two GTX 670s have a home in your PC, present or future, or is their rendering power and associated expense a burden too far?