GeForce 8400 GS 512MB vs Radeon HD 7990

Intro

Compare those specs to the Radeon HD 7990, which has a GPU core clock speed of 950 MHz, and 3072 MB of GDDR5 RAM set to run at 1500 MHz through a 384-bit bus. It also is made up of 2048 SPUs, 128 TAUs, 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 in general, due to its greater bandwidth. (explain)

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

Texel Rate

The Radeon HD 7990 will be quite a bit (about 4577%) faster with regards to anisotropic 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

The Radeon HD 7990 is quite a bit (approximately 2238%) more effective at anti-aliasing than the GeForce 8400 GS 512MB, and will be able to handle higher resolutions while still performing well. (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 maximum amount of information (measured in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the bus width by its memory clock speed. If the card has DDR type RAM, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.