GeForce 8400 GS 512MB vs Radeon HD 7990

Intro

Compare those specifications to the Radeon HD 7990, which comes with GPU core speed of 950 MHz, and 3072 MB of GDDR5 RAM set to run at 1500 MHz through a 384-bit bus. It also features 2048 SPUs, 128 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8400 GS 512MB		40 Watts
Radeon HD 7990		375 Watts
	Difference: 335 Watts (838%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 7990 is 8900% faster than the GeForce 8400 GS 512MB overall, because of its higher bandwidth. (explain)

Radeon HD 7990		576000 MB/sec
GeForce 8400 GS 512MB		6400 MB/sec
	Difference: 569600 (8900%)

Texel Rate

The Radeon HD 7990 should be much (approximately 4577%) faster with regards to texture filtering than the GeForce 8400 GS 512MB. (explain)

Radeon HD 7990		243200 Mtexels/sec
GeForce 8400 GS 512MB		5200 Mtexels/sec
	Difference: 238000 (4577%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 7990 is a better choice, and very much so. (explain)

Radeon HD 7990		60800 Mpixels/sec
GeForce 8400 GS 512MB		2600 Mpixels/sec
	Difference: 58200 (2238%)

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 data (in units of megabytes per second) that can be moved past the external memory interface within a second. The number is calculated by multiplying the card's bus width by its memory speed. In the case of DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly record to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.