Radeon HD 4650 512MB vs Radeon HD 6990

Intro

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

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4650 512MB		55 Watts
Radeon HD 6990		375 Watts
	Difference: 320 Watts (582%)

Memory Bandwidth

Theoretically, the Radeon HD 6990 should be much faster than the Radeon HD 4650 512MB overall. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 4650 512MB		16000 MB/sec
	Difference: 304000 (1900%)

Texel Rate

The Radeon HD 6990 should be much (about 730%) better at anisotropic filtering than the Radeon HD 4650 512MB. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 4650 512MB		19200 Mtexels/sec
	Difference: 140160 (730%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 6990 is superior to the Radeon HD 4650 512MB, and very much so. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 4650 512MB		4800 Mpixels/sec
	Difference: 48320 (1007%)

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 (in units of MB per second) that can be moved over the external memory interface within a second. It's worked out by multiplying the bus width by its memory clock speed. If it uses DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly record to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.