Radeon HD 3870 X2 1GB vs Radeon HD 4870 1GB

Intro

Compare all that to the Radeon HD 4870 1GB, which makes use of a 55 nm design. AMD has set the core frequency at 750 MHz. The GDDR5 memory is set to run at a frequency of 900 MHz on this particular model. It features 800(160x5) SPUs along with 40 TAUs and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 3870 X2 1GB is 25% quicker than the Radeon HD 4870 1GB in general, because of its higher data rate. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 28928 (25%)

Texel Rate

The Radeon HD 4870 1GB will be a bit (more or less 14%) better at texture filtering than the Radeon HD 3870 X2 1GB. (explain)

Radeon HD 4870 1GB		30000 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 3600 (14%)

Pixel Rate

The Radeon HD 3870 X2 1GB will be much (about 120%) more effective at full screen anti-aliasing than the Radeon HD 4870 1GB, and also will be able to handle higher screen resolutions while still performing well. (explain)

Radeon HD 3870 X2 1GB		26400 Mpixels/sec
Radeon HD 4870 1GB		12000 Mpixels/sec
	Difference: 14400 (120%)

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 maximum amount of information (measured in MB per second) that can be moved over the external memory interface within a second. It is worked out by multiplying the card's bus width by the speed of its memory. In the case of DDR type memory, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.