GeForce GT 640 DDR3 vs Radeon HD 3870 X2 1GB

Intro

Compare those specs to the Radeon HD 3870 X2 1GB, which features a clock speed of 825 MHz and a GDDR4 memory speed of 1126 MHz. It also uses a 256-bit memory bus, and makes use of a 55 nm design. It is made up of 320(64x5) SPUs, 16 TAUs, and 16 Raster Operation Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Memory Bandwidth

As far as performance goes, the Radeon HD 3870 X2 1GB should in theory be quite a bit better 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 will be just a bit (approximately 9%) more effective 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

If using high levels of AA is important to you, then the Radeon HD 3870 X2 1GB is a better choice, by a large margin. (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: Memory bandwidth is the largest amount of information (counted in megabytes per second) that can be transported across the external memory interface within a second. It's calculated by multiplying the interface width by the speed of its memory. If the card has DDR type RAM, it should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, 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 figure is worked out by multiplying the total number of texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the video 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 the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.