Radeon HD 4770 vs Radeon HD 6990

Intro

Compare all that to the Radeon HD 6990, which makes use of a 40 nm design. AMD has clocked the core frequency at 830 MHz. The GDDR5 RAM works at a speed of 1250 MHz on this specific model. It features 1536 SPUs as well as 96 TAUs and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4770		80 Watts
Radeon HD 6990		375 Watts
	Difference: 295 Watts (369%)

Memory Bandwidth

In theory, the Radeon HD 6990 should be a lot faster than the Radeon HD 4770 overall. (explain)

Radeon HD 6990		320000 MB/sec
Radeon HD 4770		51200 MB/sec
	Difference: 268800 (525%)

Texel Rate

The Radeon HD 6990 will be quite a bit (more or less 564%) more effective at AF than the Radeon HD 4770. (explain)

Radeon HD 6990		159360 Mtexels/sec
Radeon HD 4770		24000 Mtexels/sec
	Difference: 135360 (564%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 6990 is the winner, by far. (explain)

Radeon HD 6990		53120 Mpixels/sec
Radeon HD 4770		12000 Mpixels/sec
	Difference: 41120 (343%)

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: Memory bandwidth is the maximum amount of data (measured in MB per second) that can be moved across the external memory interface in one second. It's worked out by multiplying the card's bus width by the speed of its memory. In the case of DDR RAM, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics chip could possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.