Radeon HD 3870 X2 512MB vs Radeon HD 4850 512MB

Intro

Compare those specs to the Radeon HD 4850 512MB, which features GPU clock speed of 625 MHz, and 512 MB of GDDR3 memory set to run at 993 MHz through a 256-bit bus. It also is made up of 800(160x5) SPUs, 40 TAUs, 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 512MB should be much faster than the Radeon HD 4850 512MB in general. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 4850 512MB		63552 MB/sec
	Difference: 51648 (81%)

Texel Rate

The Radeon HD 3870 X2 512MB is a little bit (approximately 6%) better at texture filtering than the Radeon HD 4850 512MB. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 4850 512MB		25000 Mtexels/sec
	Difference: 1400 (6%)

Pixel Rate

The Radeon HD 3870 X2 512MB will be much (about 164%) better at AA than the Radeon HD 4850 512MB, and also will be able to handle higher screen resolutions while still performing well. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4850 512MB		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: Bandwidth is the max amount of data (measured in MB per second) that can be moved over the external memory interface in a second. It's calculated by multiplying the bus width by its memory clock speed. If it uses DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.