GeForce 8800 GTS (G80) 640MB vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which comes with a GPU core clock speed of 900 MHz, and 2048 MB of DDR3 RAM set to run at 1782 MHz through a 128-bit bus. It also is comprised of 384 SPUs, 32 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GTS (G80) 640MB		143 Watts
	Difference: 78 Watts (120%)

Memory Bandwidth

In theory, the GeForce 8800 GTS (G80) 640MB is 11% quicker than the GeForce GT 640 DDR3 in general, due to its higher bandwidth. (explain)

GeForce 8800 GTS (G80) 640MB		63360 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 6336 (11%)

Texel Rate

The GeForce GT 640 DDR3 will be a little bit (more or less 17%) more effective at anisotropic filtering than the GeForce 8800 GTS (G80) 640MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8800 GTS (G80) 640MB		24624 Mtexels/sec
	Difference: 4176 (17%)

Pixel Rate

If using a high screen resolution is important to you, then the GeForce GT 640 DDR3 is the winner, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GTS (G80) 640MB		10260 Mpixels/sec
	Difference: 4140 (40%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the largest amount of information (counted in megabytes per second) that can be moved across the external memory interface in one second. It's worked out by multiplying the card's bus width by the speed of its memory. If it uses DDR RAM, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This is worked out by multiplying the total amount of texture units of the card by the core speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.