Radeon HD 4870 2GB vs Radeon HD 6950

Intro

Compare that to the Radeon HD 6950, which comes with GPU clock speed of 800 MHz, and 1024 MB of GDDR5 RAM running at 1250 MHz through a 256-bit bus. It also features 1408 Stream Processors, 88 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 4870 2GB		150 Watts
Radeon HD 6950		200 Watts
	Difference: 50 Watts (33%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6950 should be a lot faster than the Radeon HD 4870 2GB overall. (explain)

Radeon HD 6950		160000 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 44800 (39%)

Texel Rate

The Radeon HD 6950 will be quite a bit (about 135%) more effective at anisotropic filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 6950		70400 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 40400 (135%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 6950 is superior to the Radeon HD 4870 2GB, by a large margin. (explain)

Radeon HD 6950		25600 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 13600 (113%)

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: Bandwidth is the max amount of data (in units of MB per second) that can be transferred across the external memory interface in one second. The number is worked out by multiplying the card's bus width by its memory speed. If it uses DDR type RAM, it must be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are processed per second. This number 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 graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of colour ROPs 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 rate also depends on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.