GeForce 8600 GT 512MB DDR2 vs GeForce GT 640 DDR3

Intro

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

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8600 GT 512MB DDR2		47 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 18 Watts (38%)

Memory Bandwidth

Theoretically speaking, the GeForce GT 640 DDR3 will be 346% quicker than the GeForce 8600 GT 512MB DDR2 in general, because of its higher data rate. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8600 GT 512MB DDR2		12800 MB/sec
	Difference: 44224 (346%)

Texel Rate

The GeForce GT 640 DDR3 will be a lot (approximately 233%) faster with regards to AF than the GeForce 8600 GT 512MB DDR2. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8600 GT 512MB DDR2		8640 Mtexels/sec
	Difference: 20160 (233%)

Pixel Rate

The GeForce GT 640 DDR3 is much (about 233%) better at anti-aliasing than the GeForce 8600 GT 512MB DDR2, and also should be able to handle higher screen resolutions while still performing well. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8600 GT 512MB 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: Memory bandwidth is the largest amount of information (measured in MB per second) that can be moved across the external memory interface within a second. The number is calculated by multiplying the interface width by the speed of its memory. If it uses DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card could possibly write to its local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.