GeForce 8500 GT vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which features 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 made up of 384 Stream Processors, 32 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8500 GT		45 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 20 Watts (44%)

Memory Bandwidth

As far as performance goes, the GeForce GT 640 DDR3 should theoretically be much superior to the GeForce 8500 GT overall. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8500 GT		12800 MB/sec
	Difference: 44224 (346%)

Texel Rate

The GeForce GT 640 DDR3 will be quite a bit (approximately 700%) more effective at anisotropic filtering than the GeForce 8500 GT. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8500 GT		3600 Mtexels/sec
	Difference: 25200 (700%)

Pixel Rate

If running with a high 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 8500 GT		1800 Mpixels/sec
	Difference: 12600 (700%)

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 maximum amount of information (counted in megabytes per second) that can be transported over the external memory interface in one second. It is calculated by multiplying the interface width by its memory clock speed. If the card has DDR RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed per second. This number is worked out by multiplying the total texture units by the core clock speed of the chip. The higher the texel rate, the better the graphics 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 amount of pixels that the graphics card can possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.