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

Intro

Compare those specs to the Radeon HD 4870 512MB, which uses a 55 nm design. AMD has set the core speed at 750 MHz. The GDDR5 RAM works at a frequency of 900 MHz on this card. It features 800(160x5) SPUs as well as 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

In theory, the Radeon HD 4850 X2 512MB is 10% quicker than the Radeon HD 4870 512MB overall, due to its higher bandwidth. (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 a lot (approximately 67%) more effective at anisotropic filtering 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 using high levels of AA is important to you, then the Radeon HD 4850 X2 512MB is a better choice, by far. (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 information (counted in MB per second) that can be transported past the external memory interface in a second. It is calculated by multiplying the bus width by its memory speed. In the case of DDR RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This number is worked out by multiplying the total number of texture units by the core clock 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 processed in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly record to its local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.