Radeon HD 6770 1GB vs Radeon HD 6990

Intro

Compare all of that to the Radeon HD 6990, which features a GPU core clock speed of 830 MHz, and 2048 MB of GDDR5 memory running at 1250 MHz through a 256-bit bus. It also is made up of 1536 Stream Processors, 96 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 6770 1GB		108 Watts
Radeon HD 6990		375 Watts
	Difference: 267 Watts (247%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6990 should perform much faster than the Radeon HD 6770 1GB overall. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 6770 1GB		67200 MB/sec
	Difference: 252800 (376%)

Texel Rate

The Radeon HD 6990 will be a lot (about 343%) more effective at AF than the Radeon HD 6770 1GB. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 6770 1GB		36000 Mtexels/sec
	Difference: 123360 (343%)

Pixel Rate

If using lots of anti-aliasing 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 6770 1GB		14400 Mpixels/sec
	Difference: 38720 (269%)

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 data (in units of megabytes per second) that can be transported across the external memory interface in one second. It's worked out by multiplying the bus width by its memory clock speed. If the card has DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate also depends on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.