Before we get into heavy technical details, let's get the "oooh" and "aaaah" specs on the new GeForce 8800GTS 'G80' graphics core out of the way.

NVidia's 'G80' GPU is built on TSMC's 90 nanometer manufacturing process, and it contains... get this... 681 million transistors. The Geforce 7800GTX 'G70' had 302 million transistors, and by way of comparison the ATI Radeon X1900XTX has 384 million transistors. In its current form the G80 demands a lot of power, and generates a huge amount of heat; upwards of 80W-85W under load. This is why the reference design requires such a large heatsink.

nVIDIA's 'G80' is the first DirectX 10 compatible GPU-series on the market, and it is completely different from videocards of the past. The 'G80' utilizes a unified architecture, which is another way of saying that it merges vertex and pixel shaders into one floating point processor. There have been other GPUs to take this route, notably the ATi graphics processor inside the Xbox 360, but nVIDIA is first to release this type of technology for the home PC.

The GeForce 8800GTS is based on the same G80 core that powers the GeForce 8800GTX, however nVIDIA disables a few rendering pipelines here and there along with trimming the memory bus to ensure that the GeForce 8800GTS is slower than the GTX. It's not as bad as it sounds though, GeForce 8800GTS 320MB videocard is still a wickedly fast platforms for games.

GeForce 8800GTX Core Shown

The nVIDIA GeForce 8800GTS GPU has access to six "Thread Processors" as opposed to eight with the GeForce 8800GTX. Each has 16 Stream Processors (SP) for a total 96. Gone are the hard coded Vertex and pixel shaders we're used to seeing, they have been replaced with the more flexible Stream Processor that calculates both types of data. The Stream Processors run at a blistering 1.35 GHz. Traditional core clock speeds as we know it are dead, as several internal processors are running at different speeds.

Each Thread Processor has two groups of eight SP, and each group talks to an exclusive texture address filter unit as well as well as being connected to the shared L1 cache. When more memory is needed the Thread Processor connects to the crossbar memory controller. nVIDIA's crossbar memory controller is broken up into five 64 bit chunks (six with the GeForce 8800GTX), which means the width is essentially 320 bits wide (384 bits for the 8800GX).

By moving the GPU towards a threaded design, the nvidia G80 is much more like a processor than any graphics cores of the past. Any type of data, be it pixel, vertex, or geometry shader can be processed within the SP. This allows load balancing to occur between the various tasks.

Although DirectX 9 does not support unified shader instructions, load balancing is handled automatically by the GPU so it's not something developers have to worry about. Load balancing ensures optimal performance from the GPU no matter what the situation, as pixel and vertex processing shifts greatly during game play.

While there are 96 Stream Processors broken down into 16 8-section chunks, there are only 32 texturing units total, 4 per thread processor. The texturing units run at core clock speed, and as indicated can handle 32 textures per clock. One of the most important "features" is that the texture unit operates independently of the SP, so texturing can occur at the same time as shader rendering.

One other new feature the G80 brings to the table is a stand alone video display engine completely designed for this GPU generation. Set off to the left of the G80 GPU is nVIDIA's new discrete display chip. This chip supports both TDMS logic for LCD monitors and RAMDACs for analog displays. By moving the display engine outside the GPU, it allows nVIDIA to have less overhead with multi-GPU videocards.