Radeon HD 4750 vs Radeon HD 6990

Intro

Compare that to the Radeon HD 6990, which comes with GPU core speed of 830 MHz, and 2048 MB of GDDR5 memory running at 1250 MHz through a 256-bit bus. It also features 1536 SPUs, 96 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4750		75 Watts
Radeon HD 6990		375 Watts
	Difference: 300 Watts (400%)

Memory Bandwidth

The Radeon HD 6990 should in theory be much faster than the Radeon HD 4750 in general. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 4750		51200 MB/sec
	Difference: 268800 (525%)

Texel Rate

The Radeon HD 6990 should be much (approximately 582%) better at texture filtering than the Radeon HD 4750. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 4750		23360 Mtexels/sec
	Difference: 136000 (582%)

Pixel Rate

If running with a high resolution is important to you, then the Radeon HD 6990 is the winner, by a large margin. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 4750		11680 Mpixels/sec
	Difference: 41440 (355%)

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 maximum amount of information (counted in MB per second) that can be transported across the external memory interface in one second. The number is calculated by multiplying the interface width by the speed of its memory. If the card has DDR RAM, the result should be multiplied by 2 once 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 amount of texture map elements (texels) that can be applied in one second. This number is calculated by multiplying the total number of texture units of the card 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 processed in one second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Render Output Units by the the core clock speed. 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 also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.