GeForce GT 640 DDR3 vs Radeon HD 5870

Intro

Compare all of that to the Radeon HD 5870, which has GPU core speed of 850 MHz, and 1024 MB of GDDR5 RAM set to run at 1200 MHz through a 256-bit bus. It also is made up of 1600(320x5) SPUs, 80 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 5870		188 Watts
	Difference: 123 Watts (189%)

Memory Bandwidth

Performance-wise, the Radeon HD 5870 should theoretically be a lot superior to the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 5870		153600 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 96576 (169%)

Texel Rate

The Radeon HD 5870 will be a lot (more or less 136%) better at texture filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 5870		68000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 39200 (136%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 5870 is the winner, and very much so. (explain)

Radeon HD 5870		27200 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 12800 (89%)

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 information (in units of megabytes per second) that can be transported across the external memory interface in one second. The number is calculated by multiplying the card's bus width by the speed of its memory. In the case of DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card can possibly record to the local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. 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 bandwidth is, the lower the potential to reach the maximum fill rate.