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Radeon HD 6790 vs Radeon HD 6870

Intro

The Radeon HD 6790 uses a 40 nm design. AMD has set the core frequency at 840 MHz. The GDDR5 memory works at a speed of 1050 MHz on this specific model. It features 800 SPUs along with 40 Texture Address Units and 16 ROPs.

Compare all that to the Radeon HD 6870, which has a clock speed of 900 MHz and a GDDR5 memory speed of 1050 MHz. It also uses a 256-bit bus, and uses a 40 nm design. It is made up of 1120 SPUs, 56 Texture Address Units, and 32 ROPs.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6790 150 Watts
Radeon HD 6870 151 Watts
Difference: 1 Watts (1%)

Memory Bandwidth

Both cards have the exact same bandwidth, so theoretically they should perform the same. (explain)

Texel Rate

The Radeon HD 6870 is much (about 50%) more effective at AF than the Radeon HD 6790. (explain)

Radeon HD 6870 50400 Mtexels/sec
Radeon HD 6790 33600 Mtexels/sec
Difference: 16800 (50%)

Pixel Rate

The Radeon HD 6870 will be quite a bit (more or less 114%) better at FSAA than the Radeon HD 6790, and also should be capable of handling higher resolutions without losing too much performance. (explain)

Radeon HD 6870 28800 Mpixels/sec
Radeon HD 6790 13440 Mpixels/sec
Difference: 15360 (114%)

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 6790

Amazon.com

Radeon HD 6870

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 6790 Radeon HD 6870
Manufacturer AMD AMD
Year April 2011 October 2010
Code Name Barts LE Barts XT
Fab Process 40 nm 40 nm
Bus PCIe 2.1 x16 PCIe x16
Memory 1024 MB 1024 MB
Core Speed 840 MHz 900 MHz
Shader Speed N/A MHz (N/A) MHz
Memory Speed 1050 MHz (4200 MHz effective) 1050 MHz (4200 MHz effective)
Unified Shaders 800 1120
Texture Mapping Units 40 56
Render Output Units 16 32
Bus Type GDDR5 GDDR5
Bus Width 256-bit 256-bit
DirectX Version DirectX 11 DirectX 11
OpenGL Version OpenGL 4.1 OpenGL 4.1
Power (Max TDP) 150 watts 151 watts
Shader Model 5.0 5.0
Bandwidth 134400 MB/sec 134400 MB/sec
Texel Rate 33600 Mtexels/sec 50400 Mtexels/sec
Pixel Rate 13440 Mpixels/sec 28800 Mpixels/sec

Memory Bandwidth: Memory bandwidth is the largest amount of data (in units of MB per second) that can be transferred over the external memory interface in a second. It's calculated by multiplying the interface width by its memory speed. If the card has DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card can possibly write to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.

Comments

3 Responses to “Radeon HD 6790 vs Radeon HD 6870”
[...] but the build I recomended has a much faster video card. For gaming the video card is paramount. Theoritical benchmark comparison between the 2 video cards based on specs The AMD 955 is still a heck of a [...]
[...] A graphics card that is two product cycles ahead (AMD Radeon 6870 vs the top end Mac option of the 6790); see here for a comparison of raw benchmarks from each card [...]
yoki says:
Dual-6790 or Single-6870??

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