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Radeon HD 4790 vs Radeon HD 4870 2GB

Intro

The Radeon HD 4790 has a GPU core speed of 600 MHz, and the 512 MB of GDDR5 memory runs at 800 MHz through a 256-bit bus. It also is made up of 640(128x5) Stream Processors, 32 TAUs, and 16 Raster Operation Units.

Compare those specifications to the Radeon HD 4870 2GB, which has a clock speed of 750 MHz and a GDDR5 memory speed of 900 MHz. It also makes use of a 256-bit bus, and makes use of a 55 nm design. It is made up of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 4870 2GB, in theory, should perform a little bit faster than the Radeon HD 4790 overall. (explain)

Radeon HD 4870 2GB 115200 MB/sec
Radeon HD 4790 102400 MB/sec
Difference: 12800 (13%)

Texel Rate

The Radeon HD 4870 2GB will be quite a bit (approximately 56%) better at texture filtering than the Radeon HD 4790. (explain)

Radeon HD 4870 2GB 30000 Mtexels/sec
Radeon HD 4790 19200 Mtexels/sec
Difference: 10800 (56%)

Pixel Rate

The Radeon HD 4870 2GB should be quite a bit (about 25%) more effective at FSAA than the Radeon HD 4790, and also will be able to handle higher resolutions without losing too much performance. (explain)

Radeon HD 4870 2GB 12000 Mpixels/sec
Radeon HD 4790 9600 Mpixels/sec
Difference: 2400 (25%)

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

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Radeon HD 4790

Amazon.com

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Radeon HD 4870 2GB

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 4790 Radeon HD 4870 2GB
Manufacturer AMD AMD
Year 2009 Jun 25, 2008
Code Name RV790 RV770 XT
Memory 512 MB 2048 MB
Core Speed 600 MHz 750 MHz
Memory Speed 3200 MHz 3600 MHz
Power (Max TDP) (Unknown) watts 150 watts
Bandwidth 102400 MB/sec 115200 MB/sec
Texel Rate 19200 Mtexels/sec 30000 Mtexels/sec
Pixel Rate 9600 Mpixels/sec 12000 Mpixels/sec
Unified Shaders 640(128x5) 800(160x5)
Texture Mapping Units 32 40
Render Output Units 16 16
Bus Type GDDR5 GDDR5
Bus Width 256-bit 256-bit
Fab Process 55 nm 55 nm
Transistors 959 million 956 million
Bus PCIe 2.0 x16 PCIe 2.0 x16
DirectX Version DirectX 10.1 DirectX 10.1
OpenGL Version OpenGL 3.0 OpenGL 3.0

Memory Bandwidth: Bandwidth is the max amount of data (in units of megabytes per second) that can be moved across the external memory interface in one second. It is worked out by multiplying the card's interface width by the speed of its memory. If it uses DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster 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 applied per second. This number is worked out by multiplying the total amount of texture units by the core speed of the chip. The better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip can possibly write to the local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.

Display Prices

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Radeon HD 4790

Amazon.com

Check prices at:

Radeon HD 4870 2GB

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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