Radeon HD 4890 1GB vs Radeon HD 6790

Intro

Compare all of that to the Radeon HD 6790, which comes with a core clock speed of 840 MHz and a GDDR5 memory speed of 1050 MHz. It also uses a 256-bit bus, and makes use of a 40 nm design. It features 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 1GB		190 Watts
	Difference: 40 Watts (27%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 6790 is 8% faster than the Radeon HD 4890 1GB overall, due to its higher data rate. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4890 1GB		124800 MB/sec
	Difference: 9600 (8%)

Texel Rate

The Radeon HD 4890 1GB is a bit (about 19%) better at texture filtering than the Radeon HD 6790. (explain)

Radeon HD 4890 1GB		40000 Mtexels/sec
Radeon HD 6790		33600 Mtexels/sec
	Difference: 6400 (19%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 4890 1GB is a better choice, though not by far. (explain)

Radeon HD 4890 1GB		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: Bandwidth is the maximum amount of data (counted in MB per second) that can be transported across the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the better 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 can be processed per second. This number is worked out by multiplying the total amount of texture units by the core clock 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 per second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly write to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of Render Output Units by the the core clock speed. 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 fill rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.