GeForce GT 640 DDR3 vs GeForce GTS 250 512MB

Intro

Compare that to the GeForce GTS 250 512MB, which features 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 TAUs and 16 Rasterization Operator Units.

Display Graphs

Hide Graphs

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

Theoretically speaking, the GeForce GTS 250 512MB is 23% faster than the GeForce GT 640 DDR3 overall, because of its greater bandwidth. (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 much (about 64%) more effective at AF 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, and very much so. (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: Bandwidth is the max amount of data (counted in megabytes per second) that can be moved over the external memory interface in one second. The number is calculated by multiplying the card's interface width by the speed of its memory. In the case of DDR memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, 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 number of texture map elements (texels) that can be processed per second. This number is worked out by multiplying the total number of 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 a second.

Pixel Rate: Pixel rate is the most pixels the video card could possibly record to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.