Radeon HD 4890 2GB vs Radeon HD 7770

Intro

Compare those specs to the Radeon HD 7770, which features a GPU core clock speed of 1000 MHz, and 1024 MB of GDDR5 RAM set to run at 1125 MHz through a 128-bit bus. It also features 640 Stream Processors, 40 TAUs, and 16 ROPs.

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

As far as performance goes, the Radeon HD 4890 2GB should theoretically be much superior to 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 the exact same texel fill rate, so theoretically they should be equally good at at AF. (explain)

Pixel Rate

Both cards have the exact same pixel rate, so theoretically they should perform equally good at at full screen anti-aliasing, and be capable of handling 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 maximum amount of data (in units of MB per second) that can be moved past the external memory interface in a second. The number is worked out by multiplying the bus width by its memory clock speed. If it uses DDR RAM, it should be multiplied by 2 once 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, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This is calculated by multiplying the total number of texture units by the core 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 a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly write to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the clock speed of the card. 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 is also dependant on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.