GeForce 8400 GS 512MB vs Radeon HD 6990

Intro

Compare those specs to the Radeon HD 6990, which comes with a core clock frequency of 830 MHz and a GDDR5 memory speed of 1250 MHz. It also makes use of a 256-bit bus, and makes use of a 40 nm design. It features 1536 SPUs, 96 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8400 GS 512MB		40 Watts
Radeon HD 6990		375 Watts
	Difference: 335 Watts (838%)

Memory Bandwidth

Theoretically, the Radeon HD 6990 should perform quite a bit faster than the GeForce 8400 GS 512MB overall. (explain)

Radeon HD 6990		320000 MB/sec
GeForce 8400 GS 512MB		6400 MB/sec
	Difference: 313600 (4900%)

Texel Rate

The Radeon HD 6990 is much (more or less 2965%) faster with regards to anisotropic filtering than the GeForce 8400 GS 512MB. (explain)

Radeon HD 6990		159360 Mtexels/sec
GeForce 8400 GS 512MB		5200 Mtexels/sec
	Difference: 154160 (2965%)

Pixel Rate

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

Radeon HD 6990		53120 Mpixels/sec
GeForce 8400 GS 512MB		2600 Mpixels/sec
	Difference: 50520 (1943%)

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 max amount of information (in units of megabytes per second) that can be transported over the external memory interface within a second. It is calculated by multiplying the card's bus width by the speed of its memory. In the case of DDR RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This figure is worked out by multiplying the total number of texture units by the core clock 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 video card can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the the card's 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 rate also depends on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.