GeForce GT 640 DDR3 vs Radeon HD 4870 X2

Intro

Compare those specs to the Radeon HD 4870 X2, which makes use of a 55 nm design. AMD has set the core frequency at 750 MHz. The GDDR5 RAM runs at a speed of 900 MHz on this particular card. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

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

In theory, the Radeon HD 4870 X2 should be a lot 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 will be quite a bit (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

The Radeon HD 4870 X2 is much (about 67%) better at AA than the GeForce GT 640 DDR3, and also should be able to handle higher screen resolutions without losing too much performance. (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 (in units of MB per second) that can be transported past the external memory interface in a second. It is calculated by multiplying the bus width by its memory clock speed. In the case of DDR type memory, 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 anti-aliasing, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.