Radeon HD 4890 2GB vs Radeon HD 6850

Intro

Compare all of that to the Radeon HD 6850, which has clock speeds of 775 MHz on the GPU, and 1000 MHz on the 1024 MB of GDDR5 RAM. It features 960 SPUs as well as 48 Texture Address Units and 32 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6850		127 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 63 Watts (50%)

Memory Bandwidth

In theory, the Radeon HD 6850 should be a bit faster than the Radeon HD 4890 2GB overall. (explain)

Radeon HD 6850		128000 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 3200 (3%)

Texel Rate

The Radeon HD 4890 2GB is just a bit (approximately 8%) faster with regards to anisotropic filtering than the Radeon HD 6850. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 6850		37200 Mtexels/sec
	Difference: 2800 (8%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 6850 is a better choice, by a large margin. (explain)

Radeon HD 6850		24800 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 8800 (55%)

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 maximum amount of data (counted in megabytes per second) that can be transferred across the external memory interface in a second. It is worked out by multiplying the bus width by its memory clock speed. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, 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 number of texture map elements (texels) that are processed per second. This is worked out by multiplying the total texture units of the card by the core clock 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 per second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Render Output Units by the the core 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 is also dependant 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.