Radeon HD 4850 X2 1GB vs Radeon HD 6990

Intro

Compare those specifications to the Radeon HD 6990, which comes with a core clock speed of 830 MHz and a GDDR5 memory speed of 1250 MHz. It also uses a 256-bit bus, and makes use of a 40 nm design. It is comprised of 1536 SPUs, 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

Theoretically, the Radeon HD 6990 should perform much faster than the Radeon HD 4850 X2 1GB in general. (explain)

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

Texel Rate

The Radeon HD 6990 should be quite a bit (about 219%) faster with regards to AF 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

The Radeon HD 6990 will be much (about 166%) better at anti-aliasing than the Radeon HD 4850 X2 1GB, and should be able to handle higher screen resolutions better. (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: Memory bandwidth is the maximum amount of information (counted in MB per second) that can be transferred over the external memory interface in a second. It's calculated by multiplying the interface width by its memory speed. If it uses DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. 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 processed per second. This number is worked out by multiplying the total amount of texture units 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 applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.