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Radeon HD 7770 vs Radeon HD 7870

Intro

The Radeon HD 7770 has a core clock frequency of 1000 MHz and a GDDR5 memory speed of 1125 MHz. It also makes use of a 128-bit memory bus, and uses a 28 nm design. It is comprised of 640 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Compare all that to the Radeon HD 7870, which comes with clock speeds of 1000 MHz on the GPU, and 1200 MHz on the 2048 MB of GDDR5 RAM. It features 1280 SPUs as well as 80 TAUs and 32 Rasterization Operator Units.

(No game benchmarks for this combination yet.)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7770 80 Watts
Radeon HD 7870 175 Watts
Difference: 95 Watts (119%)

Memory Bandwidth

Performance-wise, the Radeon HD 7870 should in theory be quite a bit better than the Radeon HD 7770 overall. (explain)

Radeon HD 7870 153600 MB/sec
Radeon HD 7770 72000 MB/sec
Difference: 81600 (113%)

Texel Rate

The Radeon HD 7870 should be a lot (more or less 100%) faster with regards to AF than the Radeon HD 7770. (explain)

Radeon HD 7870 80000 Mtexels/sec
Radeon HD 7770 40000 Mtexels/sec
Difference: 40000 (100%)

Pixel Rate

The Radeon HD 7870 should be much (approximately 100%) faster with regards to AA than the Radeon HD 7770, and also capable of handling higher screen resolutions without losing too much performance. (explain)

Radeon HD 7870 32000 Mpixels/sec
Radeon HD 7770 16000 Mpixels/sec
Difference: 16000 (100%)

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 7770

Amazon.com

Radeon HD 7870

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 7770 Radeon HD 7870
Manufacturer AMD AMD
Year February 2012 March 2012
Code Name Cape Verde XT Pitcairn XT
Fab Process 28 nm 28 nm
Bus PCIe 3.0 x16 PCIe 3.0 x16
Memory 1024 MB 2048 MB
Core Speed 1000 MHz 1000 MHz
Shader Speed N/A MHz (N/A) MHz
Memory Speed 1125 MHz (4500 MHz effective) 1200 MHz (4800 MHz effective)
Unified Shaders 640 1280
Texture Mapping Units 40 80
Render Output Units 16 32
Bus Type GDDR5 GDDR5
Bus Width 128-bit 256-bit
DirectX Version DirectX 11.1 DirectX 11.1
OpenGL Version OpenGL 4.2 OpenGL 4.2
Power (Max TDP) 80 watts 175 watts
Shader Model 5.0 5.0
Bandwidth 72000 MB/sec 153600 MB/sec
Texel Rate 40000 Mtexels/sec 80000 Mtexels/sec
Pixel Rate 16000 Mpixels/sec 32000 Mpixels/sec

Memory Bandwidth: Bandwidth is the largest amount of information (counted in megabytes per second) that can be transported over the external memory interface within a second. It's worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR RAM, it should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This is calculated by multiplying the total amount of texture units by the core speed of the chip. The better this number, the better the video card will be at 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 the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.

Comments

One Response to “Radeon HD 7770 vs Radeon HD 7870”
FB Appo says:
When comparing the Radeon 7870 to the 7770, there is comparisson the 7870 is way better and the 7770 is not worth investing in.

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