GeForce 8600 GT 256MB GDDR3 vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which has a core clock frequency of 900 MHz and a DDR3 memory speed of 1782 MHz. It also uses a 128-bit memory bus, and makes use of a 28 nm design. It is made up of 384 SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8600 GT 256MB GDDR3		47 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 18 Watts (38%)

Memory Bandwidth

The GeForce GT 640 DDR3 should in theory be much faster than the GeForce 8600 GT 256MB GDDR3 in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8600 GT 256MB GDDR3		22400 MB/sec
	Difference: 34624 (155%)

Texel Rate

The GeForce GT 640 DDR3 will be quite a bit (more or less 233%) faster with regards to texture filtering than the GeForce 8600 GT 256MB GDDR3. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8600 GT 256MB GDDR3		8640 Mtexels/sec
	Difference: 20160 (233%)

Pixel Rate

The GeForce GT 640 DDR3 should be much (more or less 233%) faster with regards to full screen anti-aliasing than the GeForce 8600 GT 256MB GDDR3, and also will be capable of handling higher resolutions while still performing well. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8600 GT 256MB GDDR3		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: Memory bandwidth is the largest amount of information (counted in MB per second) that can be transferred past the external memory interface in one second. It is worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR type memory, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.