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Nvidia's GeForce GTX 550 Ti graphics processor

Intrigue and fast clock rates at $149

Spectacular dual-GPU graphics cards are all well and good if you're trying to entertain your friends before taking them to the golf course in your Porsche SUV, then heading out to a five-star Thai restaurant where waiters massage your feet as you eat. The rest of us tend to shop in a more reasonable price range—you know, because silky smooth frame rates at ridiculous resolutions aren't necessarily worth missing rent.

According to Nvidia, most e-tail graphics card sales are made at the $200 price point. That's your GeForce GTX 460 1GB or GTX 560 Ti, your Radeon HD 6850 or 6950. These GPUs typically handle 1080p resolutions with ease, letting gamers sprinkle on eye candy and antialiasing as they see fit. No wonder cards of this caliber are often recommended in our system guides and deal-of-the-week posts. They're as fast as most folks are gonna need.

Some insist on seeking out cheaper alternatives, and Nvidia's latest creation caters to those penny pinchers. With a $149 suggested e-tail price, the GeForce GTX 550 Ti shouldn't put much of a dent in your credit card statement. Heck, it's affordable enough to fit into our el-cheapo Econobox build from the latest TR System Guide. Nevertheless, this newcomer should purportedly drive games happily at 1680x1050 with a smack of antialiasing, a bit like you might drive your Honda Civic to your one-bedroom apartment. It's the kind of "good enough" one might want to upgrade from... eventually.

The GeForce GTX 550 Ti, pictured above in souped-up MSI and Zotac variants, is powered by a new GF116 graphics processor. "New" is kind of a strong word, though. Nvidia has been replacing its GeForce 400-series GPUs with refreshed versions over the past several months, and this latest revamped GPU follows the same pattern. The GF116 is architecturally the same as the GF106 chip found inside the $129 GeForce GTS 450 that debuted last September, but this time around, all of the chip's key units are enabled.

We've seen this pattern before with practically all of Nvidia's graphics processors derived from the Fermi architecture. Nvidia took the earlier GPU, retained the same basic architecture and unit counts, and did extensive design work to better adapt it to TSMC's 40-nm fabrication process. The resulting GPU could tolerate higher clock speeds at lower voltages without the need to disable major portions of the chip. Thus, the GeForce GTX 460 gave way to the much faster GeForce GTX 560 Ti, to cite one example.

In the same vein, the GeForce GTX 550 Ti comes along behind the GTS 450. The GTS 450 is staying put at around $129 for now, while the GTX 550 Ti will occupy a middle ground between the GTS 450 and the GTX 460 1GB. (If you're wondering about the GeForce GTX 460 768MB and 460 SE, Nvidia says those parts are reaching end-of-life status, so they might not stick around for too long.)

The GeForce GTX 550 Ti's GF116 GPU has one graphics processing cluster with four streaming multiprocessors, each packing 48 ALUs (a.k.a. "CUDA cores" in Nvidia parlance) and a texture block capable of filtering eight texels per clock. That means 192 ALUs and 32 texels/clock in total. The GF116 rounds this off with three ROP partitions that can push a total of 24 pixels/clock, plus three 64-bit memory controllers that make up a combined 192-bit memory interface.

Those who read our GeForce GTS 450 review may recall that the GTS 450's GF106 GPU technically has the same capabilities. However, Nvidia disabled a ROP partition and the third memory controller, restricting that card to 16 pixels/clock of output and an aggregate 128-bit memory interface. The GTX 550 Ti has no such handicaps.

Two other notable attributes differentiate the GTX 550 Ti from its slower, less gifted sibling. First, base clock speeds have gone up quite a bit. Where the GTS 450 ran at 783MHz with a 1566MHz shader speed and a 900MHz GDDR5 memory clock (for an effective 3600 MT/s), the GTX 550 Ti's base spec calls for 900MHz core, 1800MHz shader, and 4104 MT/s memory speeds. Retail cards are even quicker, as we'll see in a minute.

Second, Nvidia has incorporated some special sauce that allows the GTX 550 Ti to feature an even 1GB of RAM despite its lopsided memory interface. Normally, you'd want each of a GPU's memory controllers to have the same amount of memory at its disposal. That's why cards with 192-bit memory interfaces are often seen carrying 768MB of RAM, or 256MB per memory controller. The GeForce GTX 550 Ti arranges its memory differently.

There are still six chips—two per memory controller. However, four of those are 128MB chips, while the remaining two have 256MB of capacity. In other words, two of the memory controllers shoulder 256MB each, and the third controller has 512MB all to itself. Nvidia says the GTX 550 Ti is its first ever graphics card to ship with such a mixed memory configuration. Supporting it required the implementation of custom logic in both the drivers and the GF116 GPU.

Now, given the need to balance bandwidth between the GF116's three controllers, it would appear unlikely the GTX 550 Ti is making full use of the extra 256MB on its third controller—even with drivers attempting to take advantage. This mixed memory config might therefore not be so much a technical feat as a marketing ploy, whereby the extra RAM's chief purpose could be to let Nvidia slap a nice "1GB" on the box so that the card matches up well against competing Radeons in the minds of less informed consumers. "768MB" does look a little unsightly these days, and as the company keenly pointed out while briefing us, outfitting the GTX 550 Ti with 1.5GB of RAM (512MB per controller) wouldn't have been cost-effective.

We'll see how the GTX 550 Ti scales as we crank up the resolution soon. First, though, let's have a closer look at a couple of cards.