Radeon HD 4870 2GB vs Radeon HD 6850

Intro

Compare that to the Radeon HD 6850, which comes with GPU clock speed of 775 MHz, and 1024 MB of GDDR5 RAM running at 1000 MHz through a 256-bit bus. It also is made up of 960 SPUs, 48 TAUs, 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 2GB		150 Watts
	Difference: 23 Watts (18%)

Memory Bandwidth

The Radeon HD 6850 should theoretically perform a 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 is much (more or less 24%) more effective at texture filtering 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

The Radeon HD 6850 should be quite a bit (about 107%) faster with regards to FSAA than the Radeon HD 4870 2GB, and should be able to handle higher screen resolutions without slowing down too much. (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 largest amount of information (counted in MB per second) that can be moved over the external memory interface in a second. It's worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the card's 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 amount of texture map elements (texels) that can be processed per second. This figure is worked out by multiplying the total amount of texture units by the core speed of the chip. The higher the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly write to the local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the amount of colour ROPs by the the core 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 fill rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.