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Radeon HD 4790 vs Radeon HD 4870 X2

Intro

The Radeon HD 4790 comes with clock speeds of 600 MHz on the GPU, and 800 MHz on the 512 MB of GDDR5 memory. It features 640(128x5) SPUs as well as 32 Texture Address Units and 16 ROPs.

Compare that to the Radeon HD 4870 X2, which comes with clock speeds of 750 MHz on the GPU, and 900 MHz on the 1024 MB of GDDR5 RAM. It features 800(160x5) SPUs as well as 40 Texture Address Units and 16 Rasterization Operator Units.

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Performance-wise, the Radeon HD 4870 X2 should theoretically be much better than the Radeon HD 4790 in general. (explain)

Radeon HD 4870 X2 230400 MB/sec
Radeon HD 4790 102400 MB/sec
Difference: 128000 (125%)

Texel Rate

The Radeon HD 4870 X2 is quite a bit (more or less 213%) better at texture filtering than the Radeon HD 4790. (explain)

Radeon HD 4870 X2 60000 Mtexels/sec
Radeon HD 4790 19200 Mtexels/sec
Difference: 40800 (213%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon HD 4870 X2 is the winner, by a large margin. (explain)

Radeon HD 4870 X2 24000 Mpixels/sec
Radeon HD 4790 9600 Mpixels/sec
Difference: 14400 (150%)

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 4790

Amazon.com

Check prices at:

Radeon HD 4870 X2

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.

Specifications

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Model Radeon HD 4790 Radeon HD 4870 X2
Manufacturer AMD AMD
Year 2009 Aug 12, 2008
Code Name RV790 R700
Memory 512 MB 1024 MB (x2)
Core Speed 600 MHz 750 MHz (x2)
Memory Speed 3200 MHz 3600 MHz (x2)
Power (Max TDP) (Unknown) watts 350 watts
Bandwidth 102400 MB/sec 230400 MB/sec
Texel Rate 19200 Mtexels/sec 60000 Mtexels/sec
Pixel Rate 9600 Mpixels/sec 24000 Mpixels/sec
Unified Shaders 640(128x5) 800(160x5) (x2)
Texture Mapping Units 32 40 (x2)
Render Output Units 16 16 (x2)
Bus Type GDDR5 GDDR5
Bus Width 256-bit 256-bit (x2)
Fab Process 55 nm 55 nm
Transistors 959 million 956 million
Bus PCIe 2.0 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 largest amount of information (counted in MB per second) that can be moved past the external memory interface in one second. It is worked out by multiplying the interface width by its memory speed. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.

Display Prices

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Radeon HD 4790

Amazon.com

Check prices at:

Radeon HD 4870 X2

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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