Because of design changes in the GeForce 8800 GTX chip's new architecture, we need to consider some of this card's specs differently than we have in the past. The basics are the same. The GeForce 8800 GTX has a core clock speed of 575MHz, and it comes with 768MB of DDR3 RAM clocked to 900MHz with a 1,800MHz data rate. That memory rate is a significant uptick compared to the 800MHz RAM in Nvidia's last flagship card, the GeForce 7950 GX2. But one of the main differences in the GeForce 8800 GTX's architecture lies in how we consider its pipelines.
In the past, we've said that a 3D chip has X amount of pixel pipelines and Y pipes for shader calculations. But because of the new specifications of DirectX 10, the GeForce 8800 GTX employs what's called a unified architecture. In other words, no pipe is geared toward a particular task. Instead, the GeForce 8800 GTX comes with 128 stream processors, which can dynamically process whatever info is thrown their way. This means that if your card is processing a shader-intensive scene, it can tap from more of the pipeline pool to process that image, rather than being capped at 24 or 48 pipes because some of the other pipes are set aside for geometry only. This capability should give game designers much more flexibility in how they design games, knowing that if they can balance the workload properly, they can pump a lot of processing power into a given calculation.
What's perhaps even more impressive about the GeForce 8800 GTX is its sheer horsepower. Its transistor count sits at 681 million on a 90-nanometer manufacturing process chip. That's more than the two 271-million-transistor chips on the GeForce 7950 GX2 combined. To power a single GeForce 8800 GTX card, Nvidia recommends a 450-watt power supply in a PC with a high-end dual-core chip and a typical combination of internal hardware. But the trick is that the power supply must have two PCI Express card power connectors to plug into the two sockets on the back of the card. Most modern power supplies should have the necessary connectors. If you want to add two 8800 GTX cards in an SLI configuration, however, you've got a challenge on your hands.
Nvidia hasn't released a driver that will run the GeForce 8800 GTX in SLI mode as of the time of this writing, but it may have one out soon. Thus, we didn't get to test it, but Nvidia did share the power supply specs with us. To run two GeForce 8800 GTX cards in SLI mode, Nvidia recommends at least a 750-watt power supply. But some of the recommended models on its SLI compatibility list go as high as 850 and even 1,000 watts. We suspect those higher-wattage recommendation will allow you some headroom for adding multiple hard drives and optical drivers, as well as very high-end quad-core processors. Still, it's clear that building a next-gen SLI rig will be no small undertaking, at least for now. Heck, many midtowers PC cases are too small to accept a 1,000-watt power supply.
With no DirectX 10 games available to test on at the moment, we can't speak to the GeForce 8800 GTX's next-generation performance, aside from the fact that it's the only card on the market that claims DirectX 10 compatibility. ATI's next-gen card, code-named R600, was rumored to be released in January 2007, but we haven't heard much about it so far. We imagine that ATI (whose acquisition by AMD has been finalized) will have a DirectX 10 card sooner or later, but right now Nvidia is the only vendor with something to show. And while we can't really say who will win the battle for next-generation performance, the GeForce 8800 GTX dominates every single other card on the market right now.
One of the most important things to note about the GeForce 8800 GTX and its performance is that you would be smart to pair this card with a capable monitor that can go to resolutions of 1,600x1,200 or above. Nvidia calls this XHD (extreme high definition) gaming. Whatever you want to call it, if you're not playing at high resolutions with antialiasing, anisotropic filtering, and other image-quality tweaks cranked, you'll likely hit a CPU bottleneck, which means that you're not giving the card enough to do. But when you get up to those high-quality settings, the results are amazing.