GeForce GT 420 vs Radeon HD 4890 2GB

Intro

Compare those specifications to the Radeon HD 4890 2GB, which comes with core clock speeds of 1000 MHz on the GPU, and 975 MHz on the 2048 MB of GDDR5 RAM. It features 800(160x5) SPUs along with 40 TAUs and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 420		50 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 140 Watts (280%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4890 2GB should be 333% quicker than the GeForce GT 420 in general, due to its higher bandwidth. (explain)

Radeon HD 4890 2GB		124800 MB/sec
GeForce GT 420		28800 MB/sec
	Difference: 96000 (333%)

Texel Rate

The Radeon HD 4890 2GB will be quite a bit (about 614%) better at anisotropic filtering than the GeForce GT 420. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
GeForce GT 420		5600 Mtexels/sec
	Difference: 34400 (614%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 4890 2GB is the winner, by far. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
GeForce GT 420		2800 Mpixels/sec
	Difference: 13200 (471%)

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 data (in units of MB per second) that can be moved across the external memory interface in one second. It's calculated by multiplying the card's interface width by the speed of its memory. If the card has DDR memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This is calculated by multiplying the total texture units of the card by the core clock speed of the chip. The better this number, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics card could possibly record to the local memory in a second - measured in millions of pixels per second. The number is worked out by multiplying the number of Raster Operations Pipelines by the the core 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 is also dependant on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.