Radeon HD 4890 2GB vs Radeon HD 6790

Intro

Compare those specs to the Radeon HD 6790, which comes with a clock frequency of 840 MHz and a GDDR5 memory frequency of 1050 MHz. It also uses a 256-bit memory bus, and uses a 40 nm design. It is comprised of 800 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6790		150 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 40 Watts (27%)

Memory Bandwidth

As far as performance goes, the Radeon HD 6790 should in theory be a small bit superior to the Radeon HD 4890 2GB overall. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 2GB should be just a bit (approximately 19%) more effective at AF than the Radeon HD 6790. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 6790		33600 Mtexels/sec
	Difference: 6400 (19%)

Pixel Rate

If running with lots of anti-aliasing is important to you, then the Radeon HD 4890 2GB is superior to the Radeon HD 6790, though only just barely. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 6790		13440 Mpixels/sec
	Difference: 2560 (19%)

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 moved over the external memory interface in a second. The number is calculated by multiplying the bus width by the speed of its memory. If it uses DDR type memory, 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 AA, High Dynamic Range and higher screen resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly record to the local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.