Radeon HD 4870 X2 vs Radeon HD 6850

Intro

Compare all that to the Radeon HD 6850, which makes use of a 40 nm design. AMD has set the core speed at 775 MHz. The GDDR5 memory is set to run at a speed of 1000 MHz on this card. It features 960 SPUs as well as 48 Texture Address Units and 32 ROPs.

Display Graphs

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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

Theoretically speaking, the Radeon HD 4870 X2 should be quite a bit faster than the Radeon HD 6850 overall. (explain)

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

Texel Rate

The Radeon HD 4870 X2 will be much (about 61%) faster with regards to 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

If using high levels of AA is important to you, then the Radeon HD 6850 is the winner, though not by far. (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: Bandwidth is the maximum amount of information (measured in MB per second) that can be transferred past the external memory interface within a second. It's calculated by multiplying the card's interface width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the bandwidth is, the better 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 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 the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output 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 get to the max fill rate.