GeForce 8500 GT vs GeForce GT 640 DDR3

Intro

Compare those specs to the GeForce GT 640 DDR3, which features a core clock speed of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also features a 128-bit memory bus, and uses a 28 nm design. It is made up of 384 SPUs, 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

Theoretically speaking, the GeForce GT 640 DDR3 is 346% faster than the GeForce 8500 GT overall, due to its greater bandwidth. (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 a lot (approximately 700%) better at AF 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 using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is a better choice, 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 (in units of MB per second) that can be moved past the external memory interface in a second. It is calculated by multiplying the interface width by its memory speed. If it uses DDR type RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed per second. This is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The better the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.