The nVidia G84 core has 289 million transistors, and according to nVIDIA documents a maximum power draw of 65W. That's 11W clear of what the PCI Express x16 slot can provide (maximum 75W) and why GeForce 8600GT videocards do not have an external power connector. nVidia built the 'G84' GeForce 8600GT core on Taiwan Semiconductors' 80nm manufacturing process, down from 90nm for the last generation mainstream GPU.

The clock speed of the nVidia GeForce 8600GT is set at 540 MHz, while the stream processors hum along at 1.18 GHz. The nVidia G84 core only comes equipped with 32 stream processors as opposed to 96/128 with the nVidia G80 core. The memory runs at a flat 1.4 GHz, yet with the GeForce 8600GT the memory bus width is only 128 bits. That translates into a slight memory bandwidth limitation, particularly at higher resolutions or with visual effects like AntiAliasing enabled. Maximum memory size is supposed to be 256MB for all G84 based videocards.

While the G84 core carries onward with nVidia's current thinking of how a graphics processor should be built, there are a few notable changes from the G80. Gone are the hard coded Vertex and pixel shaders, they've been replaced with a more flexible Stream Processor (or unified shader) that calculates both types of data. The Stream Processors runs at 1.18 GHz incidently. Traditional core clock speeds as we know it are dead, as several internal processors are running at different speeds.

It's important to note that the GeForce 8600GT and 8600GTS GPUs have 32 stream processors while the GeForce 8800GTS model has 96 and the 8800GTX 128. If you remember, 16 stream processors equals one thread processor, so there are only two in the nVidia G84 core.

Each Thread Processor has two groups of eight Stream Processors, 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 two 64 bit chunks for a total bus width of 128 bits. By moving the GPU towards a threaded design, the nvidia G84 is much more like a processor than any graphics core of the past. Any type of data - be it pixel, vertex, or geometry shader can be processed within the Stream Processor. This allows load balancing to occur between the various tasks.

nVidia PureVideo HD:

As for miscellaneous core technologies, by default the GeForce 8600GT supports HDCP over both DVI and HDMI although the latter connector is up to the manufacturers discretion to implement. The GeForce 8600GT model may or may not have HDCP support, that is up to individual vendors. With the release of the GeForce 8600GT core, nVIDIA is also updating its PureVideo technology. Dubbed "PureVideo HD" the videocard can now handle the entire decoding processor of HD-DVD and Blu-Ray movies. According to nVIDIA 100% of high definition video decoding can be off loaded onto the videocard at speeds of up to 40Mb/s.

As it is PureVideo HD will be of benefit to Blu-Ray/HD-DVD type movies only, and does not boost WMV9 playback at this time. That means high definition videos using the Microsoft standard will only be accelerated to previous PureVideo levels.