Radeon HD 4890 2GB vs Radeon HD 7770

Intro

Compare those specs to the Radeon HD 7770, which has GPU core speed of 1000 MHz, and 1024 MB of GDDR5 RAM set to run at 1125 MHz through a 128-bit bus. It also is made up of 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

Theoretically speaking, the Radeon HD 4890 2GB is 73% quicker than the Radeon HD 7770 overall, due to its higher data rate. (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 rate, so theoretically they should perform equally good at at AF. (explain)

Pixel Rate

Both cards have exactly the same pixel fill rate, so theoretically they should be equally good at at full screen anti-aliasing, and be able to handle the same 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 (counted in MB per second) that can be transferred past the external memory interface in one second. The number is calculated by multiplying the bus width by its memory speed. If it uses DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. 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 per second. This figure is worked out 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 video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the most pixels the video card can possibly record to the local memory in one second - measured in millions of pixels per second. The figure is worked out by multiplying the amount 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 output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the maximum fill rate.