GeForce GT 640 DDR3 vs Radeon HD 4870 X2

Intro

Compare that to the Radeon HD 4870 X2, which features a core clock speed of 750 MHz and a GDDR5 memory frequency of 900 MHz. It also uses a 256-bit bus, and makes use of a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 640 DDR3		65 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 285 Watts (438%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 should be quite a bit faster than the GeForce GT 640 DDR3 in general. (explain)

Radeon HD 4870 X2		230400 MB/sec
GeForce GT 640 DDR3		57024 MB/sec
	Difference: 173376 (304%)

Texel Rate

The Radeon HD 4870 X2 is much (more or less 108%) better at anisotropic filtering than the GeForce GT 640 DDR3. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
GeForce GT 640 DDR3		28800 Mtexels/sec
	Difference: 31200 (108%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 4870 X2 is the winner, by a large margin. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
GeForce GT 640 DDR3		14400 Mpixels/sec
	Difference: 9600 (67%)

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 max amount of information (counted in megabytes per second) that can be transferred past the external memory interface in one second. It is worked out by multiplying the card's interface width by the speed of its memory. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card could possibly write to the local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.