Nvidia has been under rare pressure recently, with ATi’s launch of the Radeon HD 3800-series finally giving it a route back into the PCs of mainstream gamers.

The cards were eminently affordable, yet fast enough to run the latest games – a boast that Nvidia’s mid-range GeForce 8600 cards couldn’t match. But ATi’s success was always going to spur Nvidia into action, and its riposte is suitably hard-hitting: the next-generation Nvidia GeForce 9600 GT.

It’s a longer card than the old 8600 GT, looking more like an 8800 GT. Like the 8800 series the GPU is a 65nm part, with 64 stream processors – twice that of the 8600’s – and it also boasts 512MB of 900MHz GDDR3 memory.

It’s the first mainstream Nvidia card to boast a 256-bit memory bus, and with a core clock of 650MHz, it’s actually very similar overall to the 8800 GTS 512MB – perhaps it’s not so next-gen after all.

We were eager to see whether the 9600 GT would be fast enough to wipe out ATi’s recent gains in one fell swoop, so we slotted it into our test rig – an X48-chipset motherboard, with a 3GHz Intel Core 2 Quad Extreme QX9650 processor and 4GB of DDR3 RAM – and put it through our demanding set of 3D benchmarks.

Crysis is the game of the moment, and the 9600 GT coasted through the first test: it achieved an average of 50fps at 1280 x 1024 and Medium settings, which puts it ahead of the 8800 GS, was almost on a par with the 8800 GT, and it nearly doubled the framerate achieved by the 8600 GTS.

Bumping the resolution up to 1600 x 1200 still produced a playable 38fps, and only when we also lifted the quality settings to High did it drop to a shaky 21fps.

In the slightly less demanding Call of Duty 4 it performed just as impressively. At 1600 x 1200 with the quality settings at their highest, it managed 50fps in our benchmark; again, that’s more than double that of the 8600 GTS, and around 25% faster than an ATi Radeon HD 3870.

It’s a huge increase in performance over the old 8600 cards, and massively repositions Nvidia’s mid-range. What once was only achievable by the upper-mid-range cards – the 8800 GT, for example, which currently retails at around $240 – is now within reach of the affordable mainstream, even if it’s not the huge architectural leap forward we might have hoped for.

Initial pricing for Gigabyte’s 9600 GT puts it at $208. This would put it below the $290 typical price of the HD 3870, and $30 below the 8800 GT, making it an absolute steal.

It’s a bold move by Nvidia, one which will surely kill off several of its existing 8-series cards in one fell swoop. But it will also put a dent in ATi’s recent resurgence, and right now that’s exactly what Nvidia needs.