Radeon HD 4850 X2 1GB vs Radeon HD 6990

Intro

Compare all of that to the Radeon HD 6990, which makes use of a 40 nm design. AMD has clocked the core speed at 830 MHz. The GDDR5 memory runs at a speed of 1250 MHz on this particular model. It features 1536 SPUs as well as 96 Texture Address Units and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4850 X2 1GB		250 Watts
Radeon HD 6990		375 Watts
	Difference: 125 Watts (50%)

Memory Bandwidth

In theory, the Radeon HD 6990 should be a lot faster than the Radeon HD 4850 X2 1GB overall. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 4850 X2 1GB		127104 MB/sec
	Difference: 192896 (152%)

Texel Rate

The Radeon HD 6990 is quite a bit (more or less 219%) more effective at anisotropic filtering than the Radeon HD 4850 X2 1GB. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 4850 X2 1GB		50000 Mtexels/sec
	Difference: 109360 (219%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 6990 is the winner, and very much so. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 4850 X2 1GB		20000 Mpixels/sec
	Difference: 33120 (166%)

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 (counted in megabytes per second) that can be transferred across the external memory interface in a second. It's worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's 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 number of texture map elements (texels) that are applied in one second. This number is worked out by multiplying the total texture units of the card by the core speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that 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 - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on many other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.