GeForce GT 640 DDR3 vs GeForce GTS 250 1GB

Intro

Compare all that to the GeForce GTS 250 1GB, which features core clock speeds of 738 MHz on the GPU, and 1100 MHz on the 1024 MB of GDDR3 RAM. It features 128 SPUs as well as 64 Texture Address Units and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
GeForce GTS 250 1GB		145 Watts
	Difference: 80 Watts (123%)

Memory Bandwidth

As far as performance goes, the GeForce GTS 250 1GB should in theory be much better than the GeForce GT 640 DDR3 in general. (explain)

GeForce GTS 250 1GB		70400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 13376 (23%)

Texel Rate

The GeForce GTS 250 1GB will be a lot (approximately 64%) better at AF than the GeForce GT 640 DDR3. (explain)

GeForce GTS 250 1GB		47232 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 18432 (64%)

Pixel Rate

If using high levels of AA is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce GTS 250 1GB, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GTS 250 1GB		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 maximum amount of data (in units of MB per second) that can be transferred across the external memory interface within a second. It is worked out by multiplying the card's bus width by the speed of its memory. If it uses DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better 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 amount of texture map elements (texels) that are applied per second. This number is calculated by multiplying the total amount of texture units by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called 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 of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.