GeForce GT 640 DDR3 vs Radeon HD 3870 X2 1GB

Intro

Compare all that to the Radeon HD 3870 X2 1GB, which has a clock frequency of 825 MHz and a GDDR4 memory frequency of 1126 MHz. It also features a 256-bit memory bus, and uses a 55 nm design. It is comprised of 320(64x5) SPUs, 16 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 3870 X2 1GB will be 153% quicker than the GeForce GT 640 DDR3 overall, because of its higher bandwidth. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 87104 (153%)

Texel Rate

The GeForce GT 640 DDR3 will be a little bit (more or less 9%) better at AF than the Radeon HD 3870 X2 1GB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 2400 (9%)

Pixel Rate

The Radeon HD 3870 X2 1GB will be much (more or less 83%) better at AA than the GeForce GT 640 DDR3, and also will be capable of handling higher screen resolutions without losing too much performance. (explain)

Radeon HD 3870 X2 1GB		26400 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 12000 (83%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the maximum amount of data (counted in megabytes per second) that can be transferred past the external memory interface within a second. It is calculated by multiplying the card's bus width by its memory speed. In the case of DDR type RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly record to the local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.