If you've been missing out on the graphics card wars of late, then here's a quick rundown. AMD launched its high-end $549 Radeon HD 7970 at the end of last year, and it reigned comfortably for a few months until NVIDIA came out with the masterful GeForce GTX 680. That would have been the end of the matter, at least for this product cycle, except for one crucial factor: time. Having reached the market so much earlier, AMD has now had six months to not only tweak its drivers but also its 28nm silicon. That process has already culminat