GeForce 8600 GTS vs GeForce GT 640 DDR3

Intro

Compare all that to the GeForce GT 640 DDR3, which features a core clock speed of 900 MHz and a DDR3 memory speed of 1782 MHz. It also features a 128-bit bus, and uses a 28 nm design. It features 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 GT 640 DDR3		65 Watts
GeForce 8600 GTS		75 Watts
	Difference: 10 Watts (15%)

Memory Bandwidth

Theoretically speaking, the GeForce GT 640 DDR3 should be 78% faster than the GeForce 8600 GTS in general, due to its greater data rate. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 8600 GTS		32000 MB/sec
	Difference: 25024 (78%)

Texel Rate

The GeForce GT 640 DDR3 will be much (more or less 167%) faster with regards to AF than the GeForce 8600 GTS. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 8600 GTS		10800 Mtexels/sec
	Difference: 18000 (167%)

Pixel Rate

The GeForce GT 640 DDR3 is quite a bit (more or less 167%) better at FSAA than the GeForce 8600 GTS, and should be capable of handling higher screen resolutions more effectively. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 8600 GTS		5400 Mpixels/sec
	Difference: 9000 (167%)

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 data (measured in megabytes per second) that can be moved over the external memory interface in one second. The number is worked out by multiplying the bus width by its memory clock speed. In the case of DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, 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 amount of texture map elements (texels) that are applied in one second. This figure is calculated by multiplying the total 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 maximum amount of pixels that the graphics card can possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.