GeForce 8800 GTX vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which makes use of a 28 nm design. nVidia has set the core frequency at 900 MHz. The DDR3 memory runs at a frequency of 1782 MHz on this specific card. It features 384 SPUs along with 32 TAUs and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce 8800 GTX		155 Watts
	Difference: 90 Watts (138%)

Memory Bandwidth

The GeForce 8800 GTX, in theory, should perform quite a bit faster than the GeForce GT 640 DDR3 in general. (explain)

GeForce 8800 GTX		86400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 29376 (52%)

Texel Rate

The GeForce 8800 GTX will be much (about 28%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce 8800 GTX		36800 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 8000 (28%)

Pixel Rate

If running with high levels of AA is important to you, then the GeForce GT 640 DDR3 is the winner, but it probably won't make a huge difference. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8800 GTX		13800 Mpixels/sec
	Difference: 600 (4%)

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: Bandwidth is the maximum amount of data (measured in megabytes per second) that can be transferred over the external memory interface within a second. The number is worked out by multiplying the bus width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one second. This is calculated by multiplying the total number 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 applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.