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Radeon HD 4790 vs Radeon HD 4870 1GB

Intro

The Radeon HD 4790 features a clock frequency of 600 MHz and a GDDR5 memory frequency of 800 MHz. It also features a 256-bit memory bus, and uses a 55 nm design. It is comprised of 640(128x5) SPUs, 32 TAUs, and 16 Raster Operation Units.

Compare all of that to the Radeon HD 4870 1GB, which uses a 55 nm design. AMD has clocked the core frequency at 750 MHz. The GDDR5 RAM is set to run at a frequency of 900 MHz on this specific model. It features 800(160x5) SPUs along with 40 Texture Address Units and 16 ROPs.

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 1GB should be 13% faster than the Radeon HD 4790 in general, because of its higher data rate. (explain)

Radeon HD 4870 1GB 115200 MB/sec
Radeon HD 4790 102400 MB/sec
Difference: 12800 (13%)

Texel Rate

The Radeon HD 4870 1GB is much (about 56%) better at AF than the Radeon HD 4790. (explain)

Radeon HD 4870 1GB 30000 Mtexels/sec
Radeon HD 4790 19200 Mtexels/sec
Difference: 10800 (56%)

Pixel Rate

The Radeon HD 4870 1GB is much (about 25%) more effective at FSAA than the Radeon HD 4790, and should be capable of handling higher resolutions while still performing well. (explain)

Radeon HD 4870 1GB 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 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 4790 Radeon HD 4870 1GB
Manufacturer AMD AMD
Year 2009 Jun 25, 2008
Code Name RV790 RV770 XT
Memory 512 MB 1024 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: Memory bandwidth is the maximum amount of data (in units of MB per second) that can be transferred across the external memory interface in a second. It is calculated by multiplying the bus width by its memory clock speed. If the card has DDR type RAM, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, 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 figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the number of Raster Operations Pipelines 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 rate also depends on many other factors, most notably the memory bandwidth of the card - the lower the 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 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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