Radeon HD 3870 X2 512MB vs Radeon HD 4790

Intro

Compare those specifications to the Radeon HD 4790, which has GPU clock speed of 600 MHz, and 512 MB of GDDR5 memory running at 800 MHz through a 256-bit bus. It also is made up of 640(128x5) SPUs, 32 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 3870 X2 512MB should be 13% quicker than the Radeon HD 4790 in general, because of its greater data rate. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 4790		102400 MB/sec
	Difference: 12800 (13%)

Texel Rate

The Radeon HD 3870 X2 512MB is quite a bit (about 38%) better at texture filtering than the Radeon HD 4790. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 7200 (38%)

Pixel Rate

The Radeon HD 3870 X2 512MB will be a lot (about 175%) faster with regards to FSAA than the Radeon HD 4790, and also should be able to handle higher resolutions without losing too much performance. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4790		9600 Mpixels/sec
	Difference: 16800 (175%)

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 transferred over the external memory interface in a second. The number is worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR type memory, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, 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 amount of texture units by the core clock speed of the chip. The better 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 the video card can possibly write to the local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.