Radeon HD 4850 X2 512MB vs Radeon HD 4870 512MB

Intro

Compare those specifications to the Radeon HD 4870 512MB, which features GPU clock speed of 750 MHz, and 512 MB of GDDR5 memory set to run 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

Power Consumption (Max TDP)

Radeon HD 4870 512MB		150 Watts
Radeon HD 4850 X2 512MB		250 Watts
	Difference: 100 Watts (67%)

Memory Bandwidth

The Radeon HD 4850 X2 512MB, in theory, should perform a little bit faster than the Radeon HD 4870 512MB in general. (explain)

Radeon HD 4850 X2 512MB		127104 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 11904 (10%)

Texel Rate

The Radeon HD 4850 X2 512MB will be much (approximately 67%) better at AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 4850 X2 512MB		50000 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 20000 (67%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 4850 X2 512MB is the winner, and very much so. (explain)

Radeon HD 4850 X2 512MB		20000 Mpixels/sec
Radeon HD 4870 512MB		12000 Mpixels/sec
	Difference: 8000 (67%)

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 max amount of data (counted in megabytes per second) that can be moved over the external memory interface within a second. It is worked out by multiplying the interface width by the speed of its memory. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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