GeForce GT 640 DDR3 vs GeForce GTX 460 2GB

Intro

Compare those specs to the GeForce GTX 460 2GB, which makes use of a 40 nm design. nVidia has clocked the core speed at 675 MHz. The GDDR5 memory works at a frequency of 900 MHz on this particular model. It features 336 SPUs along with 56 TAUs and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 460 2GB		160 Watts
	Difference: 95 Watts (146%)

Memory Bandwidth

As far as performance goes, the GeForce GTX 460 2GB should in theory be quite a bit better than the GeForce GT 640 DDR3 overall. (explain)

GeForce GTX 460 2GB		115200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 58176 (102%)

Texel Rate

The GeForce GTX 460 2GB should be much (about 31%) more effective at texture filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTX 460 2GB		37800 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 9000 (31%)

Pixel Rate

The GeForce GTX 460 2GB should be quite a bit (about 50%) more effective at anti-aliasing than the GeForce GT 640 DDR3, and also able to handle higher resolutions more effectively. (explain)

GeForce GTX 460 2GB		21600 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 7200 (50%)

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 largest amount of data (counted in MB per second) that can be moved across the external memory interface in a second. It's worked out by multiplying the card's interface width by its memory clock speed. If the card has DDR type memory, it should be multiplied by 2 again. If 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, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied in one second. This is worked out by multiplying the total number of texture units by the core clock 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 processed per second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of colour ROPs by the clock speed of the card. 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 is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.