Radeon HD 4890 2GB vs Radeon HD 7770

Intro

Compare all of that to the Radeon HD 7770, which features a core clock frequency of 1000 MHz and a GDDR5 memory frequency of 1125 MHz. It also makes use of a 128-bit bus, and uses a 28 nm design. It is comprised of 640 SPUs, 40 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7770		80 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 110 Watts (138%)

Memory Bandwidth

Performance-wise, the Radeon HD 4890 2GB should in theory be a lot better than the Radeon HD 7770 overall. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 7770		72000 MB/sec
	Difference: 52800 (73%)

Texel Rate

Both cards have exactly the same texel fill rate, so theoretically they should be equally good at at AF. (explain)

Pixel Rate

Both cards have exactly the same pixel rate, so theoretically they should perform equally good at at full screen anti-aliasing, and be able to handle the same screen resolutions. (explain)

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

Specifications

Memory Bandwidth: Memory bandwidth is the max amount of data (in units of megabytes per second) that can be moved past the external memory interface in one second. It is worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher 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 amount of texture map elements (texels) that can be processed in one second. This number is calculated by multiplying the total number of texture units of the card by the core speed of the chip. The higher the texel rate, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the most pixels the video card can possibly write to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units 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 fill rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.