Radeon HD 4850 X2 512MB vs Radeon HD 6850

Intro

Compare that to the Radeon HD 6850, which comes with a clock frequency of 775 MHz and a GDDR5 memory frequency of 1000 MHz. It also features a 256-bit memory bus, and uses a 40 nm design. It features 960 SPUs, 48 TAUs, and 32 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6850		127 Watts
Radeon HD 4850 X2 512MB		250 Watts
	Difference: 123 Watts (97%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6850 should be 1% faster than the Radeon HD 4850 X2 512MB in general, due to its higher data rate. (explain)

Radeon HD 6850		128000 MB/sec
Radeon HD 4850 X2 512MB		127104 MB/sec
	Difference: 896 (1%)

Texel Rate

The Radeon HD 4850 X2 512MB will be quite a bit (approximately 34%) better at anisotropic filtering than the Radeon HD 6850. (explain)

Radeon HD 4850 X2 512MB		50000 Mtexels/sec
Radeon HD 6850		37200 Mtexels/sec
	Difference: 12800 (34%)

Pixel Rate

The Radeon HD 6850 should be much (approximately 24%) faster with regards to full screen anti-aliasing than the Radeon HD 4850 X2 512MB, and should be capable of handling higher screen resolutions while still performing well. (explain)

Radeon HD 6850		24800 Mpixels/sec
Radeon HD 4850 X2 512MB		20000 Mpixels/sec
	Difference: 4800 (24%)

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 information (counted in MB per second) that can be transported across the external memory interface within a second. The number is calculated by multiplying the interface width by its memory speed. If the card has DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

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