Radeon HD 4870 X2 vs Radeon HD 6850

Intro

Compare all of that to the Radeon HD 6850, which has a core clock frequency of 775 MHz and a GDDR5 memory speed of 1000 MHz. It also makes use of a 256-bit bus, and uses a 40 nm design. It is comprised of 960 SPUs, 48 TAUs, and 32 Raster Operation Units.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6850		127 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 223 Watts (176%)

Memory Bandwidth

In theory, the Radeon HD 4870 X2 will be 80% quicker than the Radeon HD 6850 in general, due to its higher bandwidth. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 6850		128000 MB/sec
	Difference: 102400 (80%)

Texel Rate

The Radeon HD 4870 X2 is quite a bit (about 61%) better at texture filtering than the Radeon HD 6850. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 6850		37200 Mtexels/sec
	Difference: 22800 (61%)

Pixel Rate

The Radeon HD 6850 is a little bit (about 3%) faster with regards to full screen anti-aliasing than the Radeon HD 4870 X2, and also will be able to handle higher resolutions more effectively. (explain)

Radeon HD 6850		24800 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 800 (3%)

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 largest amount of data (counted in megabytes per second) that can be moved over the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory speed. In the case of DDR type RAM, it should 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, High Dynamic Range and high resolutions.

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

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