Radeon HD 4890 1GB vs Radeon HD 6790

Intro

Compare all that to the Radeon HD 6790, which features core speeds of 840 MHz on the GPU, and 1050 MHz on the 1024 MB of GDDR5 RAM. It features 800 SPUs as well as 40 TAUs and 16 Rasterization Operator 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 will be 8% faster than the Radeon HD 4890 1GB in general, because of its greater 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 small bit (about 19%) better at anisotropic 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

The Radeon HD 4890 1GB is just a bit (about 19%) more effective at FSAA than the Radeon HD 6790, and able to handle higher screen resolutions without slowing down too much. (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 largest amount of information (measured in megabytes per second) that can be moved over the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. 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 number of texture map elements (texels) that are processed per second. This is calculated by multiplying the total number of texture units by the core clock speed of the chip. The better this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly write to its local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of colour ROPs 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 output rate also depends on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.