GeForce GT 420 vs Radeon HD 4790

Intro

Compare those specs to the Radeon HD 4790, which makes use of a 55 nm design. AMD has set the core speed at 600 MHz. The GDDR5 RAM is set to run at a speed of 800 MHz on this model. It features 640(128x5) SPUs along with 32 TAUs and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 4790 is 256% faster than the GeForce GT 420 in general, due to its higher data rate. (explain)

Radeon HD 4790		102400 MB/sec
GeForce GT 420		28800 MB/sec
	Difference: 73600 (256%)

Texel Rate

The Radeon HD 4790 is much (about 243%) better at anisotropic filtering than the GeForce GT 420. (explain)

Radeon HD 4790		19200 Mtexels/sec
GeForce GT 420		5600 Mtexels/sec
	Difference: 13600 (243%)

Pixel Rate

The Radeon HD 4790 should be much (about 243%) more effective at full screen anti-aliasing than the GeForce GT 420, and also will be capable of handling higher resolutions without slowing down too much. (explain)

Radeon HD 4790		9600 Mpixels/sec
GeForce GT 420		2800 Mpixels/sec
	Difference: 6800 (243%)

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: Memory bandwidth is the max amount of information (measured in MB per second) that can be transported over the external memory interface within a second. It's calculated by multiplying the card's interface width by the speed of its memory. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the 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 texture map elements (texels) that are processed per second. This figure is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the 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 video card can possibly record to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.