Radeon HD 3870 X2 512MB vs Radeon HD 4790

Intro

Compare all of that to the Radeon HD 4790, which features core speeds of 600 MHz on the GPU, and 800 MHz on the 512 MB of GDDR5 memory. It features 640(128x5) SPUs as well as 32 Texture Address Units and 16 Rasterization Operator 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% faster than the Radeon HD 4790 in general, due to its higher bandwidth. (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%) faster with regards to 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 should be much (about 175%) more effective at AA than the Radeon HD 4790, and also will be capable of handling 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: Bandwidth is the maximum amount of data (counted in MB per second) that can be moved across the external memory interface within a second. The number is calculated by multiplying the card's interface width by its memory speed. If the card has DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the faster 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 number of texture map elements (texels) that are processed in one second. This figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to its local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.