GeForce GT 640 DDR3 vs Radeon HD 3870 X2 512MB

Intro

Compare those specifications to the Radeon HD 3870 X2 512MB, which has core speeds of 825 MHz on the GPU, and 900 MHz on the 512 MB of GDDR3 RAM. It features 320(64x5) SPUs along with 16 Texture Address Units and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 3870 X2 512MB should theoretically perform quite a bit faster than the GeForce GT 640 DDR3 overall. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 58176 (102%)

Texel Rate

The GeForce GT 640 DDR3 is a bit (approximately 9%) better at texture filtering than the Radeon HD 3870 X2 512MB. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3870 X2 512MB		26400 Mtexels/sec
	Difference: 2400 (9%)

Pixel Rate

If using a high resolution is important to you, then the Radeon HD 3870 X2 512MB is superior to the GeForce GT 640 DDR3, and very much so. (explain)

Radeon HD 3870 X2 512MB		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 largest amount of data (in units of megabytes per second) that can be transported past the external memory interface in one second. It's worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR memory, the result should be multiplied by 2 once again. If it uses 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 higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be processed in one second. This is calculated by multiplying the total amount of texture units by the core speed of the chip. The better the texel rate, the better the 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 maximum number of pixels the video card can possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Raster Operations Pipelines by the clock 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 fill rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the max fill rate.