GeForce GT 640 DDR3 vs GeForce GTX 550 Ti

Intro

Compare those specs to the GeForce GTX 550 Ti, which features core clock speeds of 900 MHz on the GPU, and 1026 MHz on the 1024 MB of GDDR5 memory. It features 192 SPUs as well as 32 TAUs and 24 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTX 550 Ti		116 Watts
	Difference: 51 Watts (78%)

Memory Bandwidth

Theoretically, the GeForce GTX 550 Ti should be much faster than the GeForce GT 640 DDR3 in general. (explain)

GeForce GTX 550 Ti		98496 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 41472 (73%)

Texel Rate

Both cards have the exact same texel fill rate, so in theory they should be equally good at at AF. (explain)

Pixel Rate

If running with a high screen resolution is important to you, then the GeForce GTX 550 Ti is superior to the GeForce GT 640 DDR3, by far. (explain)

GeForce GTX 550 Ti		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 maximum amount of data (counted in megabytes per second) that can be moved past the external memory interface in a second. It is calculated by multiplying the bus width by its memory clock speed. If the card has DDR type memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are applied in one second. This number is calculated by multiplying the total 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 in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines 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 quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.