GeForce GT 640 DDR3 vs Radeon HD 4870 X2

Intro

Compare all of that to the Radeon HD 4870 X2, which uses a 55 nm design. AMD has set the core frequency at 750 MHz. The GDDR5 memory runs at a frequency of 900 MHz on this particular model. It features 800(160x5) SPUs as well as 40 TAUs and 16 Rasterization Operator Units.

Display Graphs

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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

As far as performance goes, the Radeon HD 4870 X2 should theoretically be a lot superior to 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 will be much (approximately 108%) faster with regards to AF 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

The Radeon HD 4870 X2 will be much (more or less 67%) better at FSAA than the GeForce GT 640 DDR3, and also should be able to handle higher resolutions without slowing down too much. (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: Memory bandwidth is the maximum amount of data (counted in MB per second) that can be transported over the external memory interface in a second. It is worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR RAM, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the video card can possibly record to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.