A Question

Compare any two graphics cards:
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Radeon HD 4850 512MB vs Radeon HD 6850

Intro

The Radeon HD 4850 512MB uses a 55 nm design. AMD has clocked the core speed at 625 MHz. The GDDR3 RAM runs at a speed of 993 MHz on this particular card. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 Rasterization Operator Units.

Compare those specifications to the Radeon HD 6850, which features clock speeds of 775 MHz on the GPU, and 1000 MHz on the 1024 MB of GDDR5 memory. It features 960 SPUs as well as 48 TAUs and 32 Rasterization Operator Units.

Display Graphs

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(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4850 512MB 110 Watts
Radeon HD 6850 127 Watts
Difference: 17 Watts (15%)

Memory Bandwidth

The Radeon HD 6850, in theory, should perform much faster than the Radeon HD 4850 512MB overall. (explain)

Radeon HD 6850 128000 MB/sec
Radeon HD 4850 512MB 63552 MB/sec
Difference: 64448 (101%)

Texel Rate

The Radeon HD 6850 is a lot (more or less 49%) better at AF than the Radeon HD 4850 512MB. (explain)

Radeon HD 6850 37200 Mtexels/sec
Radeon HD 4850 512MB 25000 Mtexels/sec
Difference: 12200 (49%)

Pixel Rate

If using high levels of AA is important to you, then the Radeon HD 6850 is a better choice, by far. (explain)

Radeon HD 6850 24800 Mpixels/sec
Radeon HD 4850 512MB 10000 Mpixels/sec
Difference: 14800 (148%)

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.

Price Comparison

Display Prices

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Radeon HD 4850 512MB

Amazon.com

Radeon HD 6850

Amazon.com

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

Display Specifications

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Model Radeon HD 4850 512MB Radeon HD 6850
Manufacturer AMD AMD
Year Jun 25, 2008 October 2010
Code Name RV770 PRO Barts Pro
Fab Process 55 nm 40 nm
Bus PCIe 2.0 x16 PCIe x16
Memory 512 MB 1024 MB
Core Speed 625 MHz 775 MHz
Shader Speed N/A MHz (N/A) MHz
Memory Speed 1986 MHz 4000 MHz
Unified Shaders 800(160x5) 960
Texture Mapping Units 40 48
Render Output Units 16 32
Bus Type GDDR3 GDDR5
Bus Width 256-bit 256-bit
DirectX Version DirectX 10.1 DirectX 11
OpenGL Version OpenGL 3.0 OpenGL 4.1
Power (Max TDP) 110 watts 127 watts
Shader Model 4.1 5.0
Bandwidth 63552 MB/sec 128000 MB/sec
Texel Rate 25000 Mtexels/sec 37200 Mtexels/sec
Pixel Rate 10000 Mpixels/sec 24800 Mpixels/sec

Memory Bandwidth: Memory bandwidth is the max amount of data (measured in megabytes per second) that can be transported past the external memory interface in a second. It's worked out by multiplying the card's interface width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This is worked out 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 graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly write to the local memory in a second - measured in millions of pixels per second. Pixel rate 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 filling the screen with pixels (the image). 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 memory bandwidth is, the lower the potential to reach the maximum fill rate.

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