Radeon HD 4890 2GB vs Radeon HD 7970

Intro

Compare those specs to the Radeon HD 7970, which comes with a GPU core clock speed of 925 MHz, and 3072 MB of GDDR5 memory running at 1375 MHz through a 384-bit bus. It also is comprised of 2048 SPUs, 128 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 4890 2GB		190 Watts
Radeon HD 7970		250 Watts
	Difference: 60 Watts (32%)

Memory Bandwidth

Theoretically, the Radeon HD 7970 should perform quite a bit faster than the Radeon HD 4890 2GB in general. (explain)

Radeon HD 7970		264000 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 139200 (112%)

Texel Rate

The Radeon HD 7970 will be quite a bit (more or less 196%) faster with regards to AF than the Radeon HD 4890 2GB. (explain)

Radeon HD 7970		118400 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 78400 (196%)

Pixel Rate

The Radeon HD 7970 should be a lot (more or less 85%) better at full screen anti-aliasing than the Radeon HD 4890 2GB, and also should be able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 7970		29600 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 13600 (85%)

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 max amount of information (measured in megabytes per second) that can be moved across the external memory interface in a second. The number is calculated by multiplying the bus width by its memory speed. If the card has DDR type memory, the result should be multiplied by 2 again. If it uses 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, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are processed per second. This figure is calculated 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 a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - aka 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 bandwidth is, the lower the ability to get to the max fill rate.