Radeon HD 4890 2GB vs Radeon HD 7950 3GB

Intro

Compare those specifications to the Radeon HD 7950 3GB, which comes with a GPU core clock speed of 800 MHz, and 3072 MB of GDDR5 memory running at 1250 MHz through a 384-bit bus. It also features 1792 SPUs, 112 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4890 2GB		190 Watts
Radeon HD 7950 3GB		200 Watts
	Difference: 10 Watts (5%)

Memory Bandwidth

In theory, the Radeon HD 7950 3GB is 92% faster than the Radeon HD 4890 2GB overall, because of its greater bandwidth. (explain)

Radeon HD 7950 3GB		240000 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 115200 (92%)

Texel Rate

The Radeon HD 7950 3GB will be much (more or less 124%) more effective at anisotropic filtering than the Radeon HD 4890 2GB. (explain)

Radeon HD 7950 3GB		89600 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 49600 (124%)

Pixel Rate

The Radeon HD 7950 3GB should be quite a bit (more or less 60%) more effective at AA than the Radeon HD 4890 2GB, and will be capable of handling higher screen resolutions better. (explain)

Radeon HD 7950 3GB		25600 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 9600 (60%)

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 data (counted in MB per second) that can be transferred across the external memory interface in a second. It is worked out by multiplying the card's bus width by its memory speed. If it uses DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied per second. This figure is worked out by multiplying the total number of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.