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Radeon HD 4870 512MB vs Radeon HD 7850

Intro

The Radeon HD 4870 512MB comes with a core clock frequency of 750 MHz and a GDDR5 memory frequency 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 TAUs, and 16 Raster Operation Units.

Compare all that to the Radeon HD 7850, which has a GPU core clock speed of 860 MHz, and 2048 MB of GDDR5 memory running at 1200 MHz through a 256-bit bus. It also features 1024 SPUs, 64 Texture Address Units, and 32 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7850 130 Watts
Radeon HD 4870 512MB 150 Watts
Difference: 20 Watts (15%)

Memory Bandwidth

The Radeon HD 7850 should in theory perform quite a bit faster than the Radeon HD 4870 512MB in general. (explain)

Radeon HD 7850 153600 MB/sec
Radeon HD 4870 512MB 115200 MB/sec
Difference: 38400 (33%)

Texel Rate

The Radeon HD 7850 is quite a bit (about 83%) better at texture filtering than the Radeon HD 4870 512MB. (explain)

Radeon HD 7850 55040 Mtexels/sec
Radeon HD 4870 512MB 30000 Mtexels/sec
Difference: 25040 (83%)

Pixel Rate

The Radeon HD 7850 should be quite a bit (about 129%) better at AA than the Radeon HD 4870 512MB, and should be capable of handling higher resolutions without losing too much performance. (explain)

Radeon HD 7850 27520 Mpixels/sec
Radeon HD 4870 512MB 12000 Mpixels/sec
Difference: 15520 (129%)

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

Radeon HD 4870 512MB

Amazon.com

Radeon HD 7850

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

Model Radeon HD 4870 512MB Radeon HD 7850
Manufacturer AMD AMD
Year Jun 25, 2008 March 2012
Code Name RV770 XT Pitcairn Pro
Fab Process 55 nm 28 nm
Bus PCIe 2.0 x16 PCIe 3.0 x16
Memory 512 MB 2048 MB
Core Speed 750 MHz 860 MHz
Shader Speed N/A MHz (N/A) MHz
Memory Speed 900 MHz (3600 MHz effective) 1200 MHz (4800 MHz effective)
Unified Shaders 800(160x5) 1024
Texture Mapping Units 40 64
Render Output Units 16 32
Bus Type GDDR5 GDDR5
Bus Width 256-bit 256-bit
DirectX Version DirectX 10.1 DirectX 11.1
OpenGL Version OpenGL 3.0 OpenGL 4.2
Power (Max TDP) 150 watts 130 watts
Shader Model 4.1 5.0
Bandwidth 115200 MB/sec 153600 MB/sec
Texel Rate 30000 Mtexels/sec 55040 Mtexels/sec
Pixel Rate 12000 Mpixels/sec 27520 Mpixels/sec

Memory Bandwidth: Memory bandwidth is the maximum amount of data (counted in megabytes per second) that can be moved over the external memory interface in one second. It's worked out by multiplying the bus width by its memory speed. In the case of DDR type memory, it must be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied in one second. This figure is worked out by multiplying the total number of texture units by the core clock 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 in a second.

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

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