Radeon HD 4850 X2 512MB vs Radeon HD 6850

Intro

Compare those specifications to the Radeon HD 6850, which has a core clock frequency of 775 MHz and a GDDR5 memory frequency of 1000 MHz. It also features a 256-bit bus, and makes use of a 40 nm design. It is made up of 960 SPUs, 48 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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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

In theory, the Radeon HD 6850 will be 1% faster than the Radeon HD 4850 X2 512MB overall, because of its greater bandwidth. (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 is a lot (about 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 will be quite a bit (about 24%) more effective at full screen anti-aliasing than the Radeon HD 4850 X2 512MB, and also should be able to handle higher screen resolutions more effectively. (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 data (in units of megabytes per second) that can be moved past the external memory interface within a second. It's worked out by multiplying the 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 4 instead. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This figure is calculated by multiplying the total texture units by the core speed of the chip. The better this number, the better the graphics 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 maximum amount of pixels the video card could possibly record to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. 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 lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.