Radeon HD 3850 256MB vs Radeon HD 3870 X2 512MB

Intro

Compare all that to the Radeon HD 3870 X2 512MB, which features a core clock speed of 825 MHz and a GDDR3 memory speed of 900 MHz. It also makes use of a 256-bit memory bus, and uses a 55 nm design. It is comprised of 320(64x5) SPUs, 16 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 3870 X2 512MB, in theory, should be a lot faster than the Radeon HD 3850 256MB overall. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 3850 256MB		52992 MB/sec
	Difference: 62208 (117%)

Texel Rate

The Radeon HD 3870 X2 512MB is much (about 147%) more effective at texture filtering than the Radeon HD 3850 256MB. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 3850 256MB		10688 Mtexels/sec
	Difference: 15712 (147%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 3870 X2 512MB is a better choice, and very much so. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 3850 256MB		10688 Mpixels/sec
	Difference: 15712 (147%)

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 maximum amount of information (counted in MB per second) that can be moved across the external memory interface within a second. It's calculated by multiplying the interface width by the speed of its memory. If the card has DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen 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 amount of texture units of the card by the core clock speed of the chip. The higher this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly record to the local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.