GeForce 8600 GT 1GB DDR2 vs GeForce GT 640 DDR3

Intro

Compare all that to the GeForce GT 640 DDR3, which comes with a clock frequency of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also makes use of a 128-bit bus, and uses a 28 nm design. It is comprised of 384 SPUs, 32 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8600 GT 1GB DDR2		47 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 18 Watts (38%)

Memory Bandwidth

The GeForce GT 640 DDR3 should theoretically be much faster than the GeForce 8600 GT 1GB DDR2 in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8600 GT 1GB DDR2		12800 MB/sec
	Difference: 44224 (346%)

Texel Rate

The GeForce GT 640 DDR3 will be quite a bit (approximately 233%) faster with regards to texture filtering than the GeForce 8600 GT 1GB DDR2. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8600 GT 1GB DDR2		8640 Mtexels/sec
	Difference: 20160 (233%)

Pixel Rate

The GeForce GT 640 DDR3 will be quite a bit (about 233%) better at AA than the GeForce 8600 GT 1GB DDR2, and also capable of handling higher resolutions without losing too much performance. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8600 GT 1GB DDR2		4320 Mpixels/sec
	Difference: 10080 (233%)

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 information (in units of megabytes per second) that can be moved across the external memory interface within a second. It's calculated by multiplying the bus width by its memory speed. In the case of DDR type RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the 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 in one second. This figure is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The higher the texel rate, 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 write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.