Radeon HD 4870 2GB vs Radeon HD 6850

Intro

Compare that to the Radeon HD 6850, which has a clock speed of 775 MHz and a GDDR5 memory speed of 1000 MHz. It also features a 256-bit bus, and makes use of a 40 nm design. It features 960 SPUs, 48 TAUs, 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 4870 2GB		150 Watts
	Difference: 23 Watts (18%)

Memory Bandwidth

The Radeon HD 6850 should theoretically be a little bit faster than the Radeon HD 4870 2GB overall. (explain)

Radeon HD 6850		128000 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 12800 (11%)

Texel Rate

The Radeon HD 6850 should be quite a bit (approximately 24%) better at AF than the Radeon HD 4870 2GB. (explain)

Radeon HD 6850		37200 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 7200 (24%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 6850 is the winner, and very much so. (explain)

Radeon HD 6850		24800 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 12800 (107%)

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.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the max amount of data (measured in megabytes per second) that can be moved past the external memory interface in a second. It's worked out by multiplying the bus width by its memory speed. If it uses DDR memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly write to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.