Radeon HD 4870 1GB vs Radeon HD 6950 2GB

Intro

Compare all that to the Radeon HD 6950 2GB, which has core clock speeds of 800 MHz on the GPU, and 1250 MHz on the 2048 MB of GDDR5 RAM. It features 1408 SPUs along with 88 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 4870 1GB		150 Watts
Radeon HD 6950 2GB		200 Watts
	Difference: 50 Watts (33%)

Memory Bandwidth

In theory, the Radeon HD 6950 2GB is 39% quicker than the Radeon HD 4870 1GB overall, due to its greater data rate. (explain)

Radeon HD 6950 2GB		160000 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 44800 (39%)

Texel Rate

The Radeon HD 6950 2GB is much (approximately 135%) more effective at AF than the Radeon HD 4870 1GB. (explain)

Radeon HD 6950 2GB		70400 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 40400 (135%)

Pixel Rate

The Radeon HD 6950 2GB will be much (more or less 113%) better at full screen anti-aliasing than the Radeon HD 4870 1GB, and also will be able to handle higher screen resolutions without losing too much performance. (explain)

Radeon HD 6950 2GB		25600 Mpixels/sec
Radeon HD 4870 1GB		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 largest amount of data (in units of MB per second) that can be transferred past the external memory interface within a second. It is worked out by multiplying the bus width by its memory speed. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This figure is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the video 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 chip could possibly write to its 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 - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.