GeForce GT 640 DDR3 vs GeForce GTS 250 512MB

Intro

Compare those specifications to the GeForce GTS 250 512MB, which has clock speeds of 738 MHz on the GPU, and 1100 MHz on the 512 MB of GDDR3 memory. It features 128 SPUs as well as 64 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 GTS 250 512MB		145 Watts
	Difference: 80 Watts (123%)

Memory Bandwidth

The GeForce GTS 250 512MB should theoretically be quite a bit faster than the GeForce GT 640 DDR3 in general. (explain)

GeForce GTS 250 512MB		70400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 13376 (23%)

Texel Rate

The GeForce GTS 250 512MB will be a lot (approximately 64%) faster with regards to anisotropic filtering than the GeForce GT 640 DDR3. (explain)

GeForce GTS 250 512MB		47232 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 18432 (64%)

Pixel Rate

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

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GTS 250 512MB		11808 Mpixels/sec
	Difference: 2592 (22%)

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 (in units of megabytes per second) that can be moved past the external memory interface in a second. It's calculated by multiplying the bus width by its memory clock speed. In the case of DDR 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 AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.