Radeon HD 4790 vs Radeon HD 6990

Intro

Compare all of that to the Radeon HD 6990, which features core speeds of 830 MHz on the GPU, and 1250 MHz on the 2048 MB of GDDR5 memory. It features 1536 SPUs along with 96 Texture Address Units and 32 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically, the Radeon HD 6990 should be much faster than the Radeon HD 4790 overall. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 4790		102400 MB/sec
	Difference: 217600 (213%)

Texel Rate

The Radeon HD 6990 is a lot (more or less 730%) better at AF than the Radeon HD 4790. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 140160 (730%)

Pixel Rate

The Radeon HD 6990 should be quite a bit (more or less 453%) faster with regards to anti-aliasing than the Radeon HD 4790, and also able to handle higher screen resolutions better. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 4790		9600 Mpixels/sec
	Difference: 43520 (453%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the largest amount of information (measured in megabytes per second) that can be transported past the external memory interface in one second. It is worked out by multiplying the interface width by the speed of its memory. If it uses DDR RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly record to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill 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.