GeForce 820M vs Radeon HD 4790

Intro

Compare that to the Radeon HD 4790, which has GPU clock speed of 600 MHz, and 512 MB of GDDR5 memory set to run at 800 MHz through a 256-bit bus. It also is comprised of 640(128x5) SPUs, 32 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 4790 should be much faster than the GeForce 820M overall. (explain)

Radeon HD 4790		102400 MB/sec
GeForce 820M		16000 MB/sec
	Difference: 86400 (540%)

Texel Rate

The Radeon HD 4790 will be much (approximately 67%) more effective at anisotropic filtering than the GeForce 820M. (explain)

Radeon HD 4790		19200 Mtexels/sec
GeForce 820M		11504 Mtexels/sec
	Difference: 7696 (67%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 4790 is the winner, and very much so. (explain)

Radeon HD 4790		9600 Mpixels/sec
GeForce 820M		2876 Mpixels/sec
	Difference: 6724 (234%)

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 data (counted in MB per second) that can be transported over the external memory interface within a second. The number is calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This figure is worked out by multiplying the total number of texture units 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 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. Pixel rate is worked out by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.