GeForce GT 640 DDR3 vs Radeon HD 3870 512MB

Intro

Compare all of that to the Radeon HD 3870 512MB, which has clock speeds of 775 MHz on the GPU, and 900 MHz on the 512 MB of GDDR3 memory. It features 320(64x5) SPUs along with 16 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
Radeon HD 3870 512MB		106 Watts
	Difference: 41 Watts (63%)

Memory Bandwidth

The Radeon HD 3870 512MB should theoretically be a little bit faster than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 3870 512MB		57600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 576 (1%)

Texel Rate

The GeForce GT 640 DDR3 will be much (more or less 132%) better at anisotropic filtering than the Radeon HD 3870 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3870 512MB		12400 Mtexels/sec
	Difference: 16400 (132%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is superior to the Radeon HD 3870 512MB, but it probably won't make a huge difference. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
Radeon HD 3870 512MB		12400 Mpixels/sec
	Difference: 2000 (16%)

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 moved across the external memory interface in a second. It is calculated by multiplying the interface width by its memory speed. If it uses DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied in one second. This figure is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels per 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 calculated by multiplying the amount of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate is also dependant on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.