Radeon HD 3870 X2 1GB vs Radeon HD 4850 2GB

Intro

Compare all of that to the Radeon HD 4850 2GB, which features GPU clock speed of 625 MHz, and 2048 MB of GDDR4 RAM set to run at 993 MHz through a 256-bit bus. It also is comprised of 800(160x5) SPUs, 40 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 1GB should be 127% faster than the Radeon HD 4850 2GB in general, because of its higher bandwidth. (explain)

Radeon HD 3870 X2 1GB		144128 MB/sec
Radeon HD 4850 2GB		63552 MB/sec
	Difference: 80576 (127%)

Texel Rate

The Radeon HD 3870 X2 1GB should be just a bit (approximately 6%) faster with regards to AF than the Radeon HD 4850 2GB. (explain)

Radeon HD 3870 X2 1GB		26400 Mtexels/sec
Radeon HD 4850 2GB		25000 Mtexels/sec
	Difference: 1400 (6%)

Pixel Rate

If using a high resolution is important to you, then the Radeon HD 3870 X2 1GB is superior to the Radeon HD 4850 2GB, and very much so. (explain)

Radeon HD 3870 X2 1GB		26400 Mpixels/sec
Radeon HD 4850 2GB		10000 Mpixels/sec
	Difference: 16400 (164%)

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 information (counted in MB per second) that can be transferred over the external memory interface in one second. It's worked out by multiplying the bus width by its memory speed. 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 better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card can possibly record to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel 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 potential to get to the max fill rate.