GeForce GT 640 DDR3 vs Radeon HD 3850 X2

Intro

Compare those specs to the Radeon HD 3850 X2, which features a clock frequency of 668 MHz and a GDDR3 memory frequency of 828 MHz. It also features a 256-bit bus, and uses a 55 nm design. It features 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 3850 X2 should be 86% quicker than the GeForce GT 640 DDR3 in general, due to its greater data rate. (explain)

Radeon HD 3850 X2		105984 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 48960 (86%)

Texel Rate

The GeForce GT 640 DDR3 is a lot (approximately 35%) better at AF than the Radeon HD 3850 X2. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
Radeon HD 3850 X2		21376 Mtexels/sec
	Difference: 7424 (35%)

Pixel Rate

The Radeon HD 3850 X2 will be much (approximately 48%) more effective at AA than the GeForce GT 640 DDR3, and also should be capable of handling higher resolutions without losing too much performance. (explain)

Radeon HD 3850 X2		21376 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 6976 (48%)

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 (measured in megabytes per second) that can be transported past the external memory interface in one second. It's calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR type RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, 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 can be processed per second. This is calculated by multiplying the total texture units of the card by the core speed of the chip. The higher the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.