GeForce 820M vs Radeon HD 4790

Intro

Compare those specs to the Radeon HD 4790, which has a clock frequency of 600 MHz and a GDDR5 memory frequency of 800 MHz. It also makes use of a 256-bit memory bus, and makes use of a 55 nm design. It features 640(128x5) SPUs, 32 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

As far as performance goes, the Radeon HD 4790 should in theory be quite a bit better than the GeForce 820M in general. (explain)

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

Texel Rate

The Radeon HD 4790 should be a lot (approximately 67%) faster with regards to AF than the GeForce 820M. (explain)

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

Pixel Rate

The Radeon HD 4790 will be a lot (approximately 234%) faster with regards to FSAA than the GeForce 820M, and will be able to handle higher screen resolutions while still performing well. (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 max amount of information (counted in megabytes per second) that can be transported over the external memory interface in one second. The number is worked out by multiplying the interface width by its memory speed. If it uses DDR type RAM, it should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed per second. This figure is worked out by multiplying the total texture units 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 processed in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount 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 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 potential to reach the max fill rate.