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Radeon HD 3870 X2 512MB vs Radeon HD 4850 X2 1GB

Intro

The Radeon HD 3870 X2 512MB features a GPU clock speed of 825 MHz, and the 512 MB of GDDR3 memory is set to run at 900 MHz through a 256-bit bus. It also features 320(64x5) SPUs, 16 Texture Address Units, and 16 ROPs.

Compare those specifications to the Radeon HD 4850 X2 1GB, which makes use of a 55 nm design. AMD has clocked the core frequency at 625 MHz. The GDDR3 memory is set to run at a speed of 993 MHz on this specific model. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 ROPs.

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 4850 X2 1GB is 10% faster than the Radeon HD 3870 X2 512MB overall, due to its greater bandwidth. (explain)

Radeon HD 4850 X2 1GB 127104 MB/sec
Radeon HD 3870 X2 512MB 115200 MB/sec
Difference: 11904 (10%)

Texel Rate

The Radeon HD 4850 X2 1GB is much (more or less 89%) more effective at texture filtering than the Radeon HD 3870 X2 512MB. (explain)

Radeon HD 4850 X2 1GB 50000 Mtexels/sec
Radeon HD 3870 X2 512MB 26400 Mtexels/sec
Difference: 23600 (89%)

Pixel Rate

The Radeon HD 3870 X2 512MB should be quite a bit (approximately 32%) more effective at anti-aliasing than the Radeon HD 4850 X2 1GB, and also will be able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 3870 X2 512MB 26400 Mpixels/sec
Radeon HD 4850 X2 1GB 20000 Mpixels/sec
Difference: 6400 (32%)

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

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Radeon HD 3870 X2 512MB

Amazon.com

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Radeon HD 4850 X2 1GB

Amazon.com

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Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

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Model Radeon HD 3870 X2 512MB Radeon HD 4850 X2 1GB
Manufacturer AMD AMD
Year Jan 28, 2008 Nov 7, 2008
Code Name R680 R700
Memory 512 MB (x2) 1024 MB (x2)
Core Speed 825 MHz (x2) 625 MHz (x2)
Memory Speed 1800 MHz (x2) 1986 MHz (x2)
Power (Max TDP) (Unknown) watts 250 watts
Bandwidth 115200 MB/sec 127104 MB/sec
Texel Rate 26400 Mtexels/sec 50000 Mtexels/sec
Pixel Rate 26400 Mpixels/sec 20000 Mpixels/sec
Unified Shaders 320(64x5) (x2) 800(160x5) (x2)
Texture Mapping Units 16 (x2) 40 (x2)
Render Output Units 16 (x2) 16 (x2)
Bus Type GDDR3 GDDR3
Bus Width 256-bit (x2) 256-bit (x2)
Fab Process 55 nm 55 nm
Transistors (Unknown) million 956 million
Bus PCIe 2.0 x16/(internal PCIe 1.1 x16) PCIe 2.0 x16 (PCIe bridge)
DirectX Version DirectX 10.1 DirectX 10.1
OpenGL Version OpenGL 3.0 OpenGL 3.0

Memory Bandwidth: Bandwidth is the max amount of information (counted in megabytes per second) that can be moved across the external memory interface in one second. The number is calculated by multiplying the interface width by its memory speed. In the case of DDR type memory, it should be multiplied by 2 again. If it uses 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 high resolutions.

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

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly write to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.

Display Prices

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Radeon HD 3870 X2 512MB

Amazon.com

Check prices at:

Radeon HD 4850 X2 1GB

Amazon.com

Check prices at:

Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

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