Single page Print

NVIDIA's GeForce 7800 GTX 512 graphics processor


An Ultra by any other name...
— 8:00 AM on November 14, 2005

EVERY ONCE IN A WHILE as a writer, you have to dig deep into the imagery file in order to do a subject justice. Such is the case with the GeForce 7800 GTX 512, an amped-up version of NVIDIA's top-end GPU that's much more than just a familiar product with additional memory. Let's see what I have in here.

Car analogy? Check.

Veiled profanity? Check.

Pro wrestling terms? Check.

Edgy pop-cultural reference? Check.

Looks like we're all set.

This new 512MB version of the GeForce 7800 GTX, you see, doesn't run at the 430MHz GPU and 1.2GHz memory clocks that the standard version does. Oh, no. This card is intended to compete with—nay, embarrass—ATI's ultra-high-end Radeon X1800 XT, the recently crowned king of single-card graphics performance. NVIDIA's not calling it an Ultra, but they might as well be, with clock speeds of 550MHz for the GPU and 1.7GHz for the memory. That, my friend, is fast. We're talking about 13.2 gigatexels per second of fill rate and over 54GB per second of memory bandwidth. Those towering specifications could allow this Bugatti Veyron of the graphics world to lay the freaking smack down on the Radeon X1800 XT. And the prospect of running a couple of these monsters in SLI captures the geek's imagination like a wayward pair of Carolina Panthers cheerleaders.

We have, of course, subjected the GeForce 7800 GTX 512 to a grueling battery of performance tests using the latest games at a range of resolutions, including the sick and disturbing 2048x1536, just because we could. Can NVIDIA's new $649 beast show up ATI's Radeon X1800 XT? Will a pair of these in running in tandem cause the lights to dim in Damage Labs? We're about to find out.

Holy crap
Not to put too fine a point on it, but this thing is downright scary. The GeForce 7800 GTX 512 comes with the same G70 graphics processor that powers the 256MB version of the 7800 GTX, complete with 24 pixel shader pipes, 24 texture units, and very strong clock-for-clock performance. However, NVIDIA says 7800 GTX 512 cards will come with a new stepping of the chip, also built at TSMC on a 110nm process, but made with fabrication process tweaks intended to allow for higher clock speeds. Also on the cards is 512MB of GDDR3 memory running at a nominal clock speed of 850MHz, yielding a 1.7GHz effective data rate.

The basic math here portends good things from this new card. The Radeon X1800 XT, 625MHz screamer that it is, has "only" 10 gigatexels per second of fill rate and 48GB per second of memory bandwidth, versus 13.2 gigatexels/s and 54.4GB/s for the 7800 GTX 512. Since multitextured fill rate roughly corresponds to pixel shading power in both of these architectures, the new NVIDIA card looks poised to retake the performance crown for the green team.

Speaking of looking poised, have a gander at the cooler on this puppy.


The GeForce 7800 GTX 512


Fan and heatpipes up close


Makes even the Radeon X1800 XT look small

As you might have expected, the 7800 GTX 512 has a double-wide cooler strapped to it, but you may not have expected something quite this elaborate, given the relatively modest single-slot cooler attached to the 256MB versions of the card. This cooler has its origins in NVIDIA's workstation-class Quadro line, and it combines multiple heatpipes with a large-diameter fan in order to deliver the maximum amount of cooling with a minimum of noise.

Pry off that heatsink, and underneath you'll find a couple of interesting items.


First, there's the GPU, marked with a tell-tale "7800-U". Among other words, "Ultra" happens to start with U. Coincidence? We report; you decide.


Next, there are the Samsung GDDR3 memory chips, rated to a jaw-dropping 900MHz. NVIDIA says the 850MHz memory clock speed on its 7800 GTX 512 reference cards is conservative, and we may well see "overclocked in the box" cards testing the limits of the memory's rated speeds. We may also see overclocked out-of-the-box versions of the same, if we flip over to page 12.

NVIDIA says the 7800 GTX 512 pulls about 120W of juice at peak, up from 100W on the vanilla 7800 GTX. That leaves it in the same basic territory in terms of power supplies. They're recommending a 350W unit for a single card and a 500W unit for SLI. I'm recommending you strap on the Depends as we turn our attention to the benchmark results.