Radeon HD 3870 X2 1GB vs Radeon HD 4870 X2

Intro

Compare those specifications to the Radeon HD 4870 X2, which uses a 55 nm design. AMD has set the core frequency at 750 MHz. The GDDR5 memory runs at a speed of 900 MHz on this model. It features 800(160x5) SPUs as well as 40 TAUs and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 should be 60% quicker than the Radeon HD 3870 X2 1GB overall, because of its greater data rate. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 3870 X2 1GB		144128 MB/sec
	Difference: 86272 (60%)

Texel Rate

The Radeon HD 4870 X2 will be a lot (about 127%) more effective at texture filtering than the Radeon HD 3870 X2 1GB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 3870 X2 1GB		26400 Mtexels/sec
	Difference: 33600 (127%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon HD 3870 X2 1GB is superior to the Radeon HD 4870 X2, not by a very large margin though. (explain)

Radeon HD 3870 X2 1GB		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: Bandwidth is the maximum amount of data (measured in megabytes per second) that can be moved past the external memory interface in one second. The number is calculated by multiplying the bus width by its memory clock speed. In the case of DDR type memory, it must be multiplied by 2 again. If 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, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied per second. This is calculated by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the video 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 maximum number of pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.