Radeon HD 3870 X2 512MB vs Radeon HD 4870 X2

Intro

Compare all of that to the Radeon HD 4870 X2, which has GPU core speed of 750 MHz, and 1024 MB of GDDR5 memory running at 900 MHz through a 256-bit bus. It also features 800(160x5) SPUs, 40 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 4870 X2 should in theory perform a lot faster than the Radeon HD 3870 X2 512MB overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 3870 X2 512MB		115200 MB/sec
	Difference: 115200 (100%)

Texel Rate

The Radeon HD 4870 X2 will be quite a bit (about 127%) better at texture filtering than the Radeon HD 3870 X2 512MB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 3870 X2 512MB		26400 Mtexels/sec
	Difference: 33600 (127%)

Pixel Rate

If running with a high resolution is important to you, then the Radeon HD 3870 X2 512MB is superior to the Radeon HD 4870 X2, not by a very large margin though. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 2400 (10%)

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 largest amount of data (in units of MB per second) that can be transported across the external memory interface in a second. The number is calculated by multiplying the card's interface width by its memory speed. If it uses DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's 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 texture map elements (texels) that can be processed per second. This figure is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

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