GeForce GTX 660 vs Radeon HD 3870 X2 512MB

Intro

Compare those specs to the Radeon HD 3870 X2 512MB, which features GPU core speed of 825 MHz, and 512 MB of GDDR3 memory running at 900 MHz through a 256-bit bus. It also is made up of 320(64x5) Stream Processors, 16 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

The GeForce GTX 660 should in theory perform quite a bit faster than the Radeon HD 3870 X2 512MB overall. (explain)

GeForce GTX 660		144192 MB/sec
Radeon HD 3870 X2 512MB		115200 MB/sec
	Difference: 28992 (25%)

Texel Rate

The GeForce GTX 660 will be much (about 197%) faster with regards to anisotropic filtering than the Radeon HD 3870 X2 512MB. (explain)

GeForce GTX 660		78400 Mtexels/sec
Radeon HD 3870 X2 512MB		26400 Mtexels/sec
	Difference: 52000 (197%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 3870 X2 512MB is a better choice, though only just barely. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
GeForce GTX 660		23520 Mpixels/sec
	Difference: 2880 (12%)

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: Memory bandwidth is the max amount of data (in units of MB per second) that can be transported past the external memory interface within a second. The number is calculated by multiplying the bus width by its memory clock speed. In the case of DDR type memory, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better 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 amount of texture map elements (texels) that are applied in one second. This 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 texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on many 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.