Radeon HD 4890 1GB vs Radeon HD 6790

Intro

Compare those specifications 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 along with 40 Texture Address Units 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

The Radeon HD 6790 should in theory perform a small bit faster than the Radeon HD 4890 1GB overall. (explain)

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

Texel Rate

The Radeon HD 4890 1GB will be just a bit (more or less 19%) more effective 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 running with a high screen resolution is important to you, then the Radeon HD 4890 1GB is the winner, 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 information (in units of megabytes per second) that can be transported over the external memory interface in a second. It's worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR memory, it should be multiplied by 2 once 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, 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 number is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The better this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.