GeForce GT 640 DDR3 vs Radeon HD 3870 X2 1GB

Intro

Compare those specs to the Radeon HD 3870 X2 1GB, which uses a 55 nm design. AMD has clocked the core speed at 825 MHz. The GDDR4 RAM is set to run at a frequency of 1126 MHz on this specific card. 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

Theoretically speaking, the Radeon HD 3870 X2 1GB should perform much faster than the GeForce GT 640 DDR3 in general. (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 is just a bit (about 9%) better at texture filtering 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 a lot (more or less 83%) more effective at FSAA than the GeForce GT 640 DDR3, and able to handle higher screen resolutions more effectively. (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 largest amount of information (measured in MB per second) that can be transported past the external memory interface within a second. It is calculated by multiplying the card's interface width by the speed of its memory. In the case of DDR memory, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to its local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the the card's 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 rate also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.