GeForce GT 420 vs Radeon HD 7850

Intro

Compare that to the Radeon HD 7850, which comes with a GPU core clock speed of 860 MHz, and 2048 MB of GDDR5 memory set to run at 1200 MHz through a 256-bit bus. It also is comprised of 1024 Stream Processors, 64 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 420		50 Watts
Radeon HD 7850		130 Watts
	Difference: 80 Watts (160%)

Memory Bandwidth

In theory, the Radeon HD 7850 should be a lot faster than the GeForce GT 420 in general. (explain)

Radeon HD 7850		153600 MB/sec
GeForce GT 420		28800 MB/sec
	Difference: 124800 (433%)

Texel Rate

The Radeon HD 7850 will be much (about 883%) more effective at texture filtering than the GeForce GT 420. (explain)

Radeon HD 7850		55040 Mtexels/sec
GeForce GT 420		5600 Mtexels/sec
	Difference: 49440 (883%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 7850 is a better choice, and very much so. (explain)

Radeon HD 7850		27520 Mpixels/sec
GeForce GT 420		2800 Mpixels/sec
	Difference: 24720 (883%)

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 (counted in megabytes per second) that can be transferred across the external memory interface within a second. The number is worked out by multiplying the interface width by its memory clock speed. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This number is calculated by multiplying the total number of texture units of the card by the core 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 per second.

Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly record to its local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.