GeForce GT 420 vs Radeon HD 7850

Intro

Compare that to the Radeon HD 7850, which comes with a clock speed of 860 MHz and a GDDR5 memory speed of 1200 MHz. It also uses a 256-bit bus, and uses a 28 nm design. It is made up of 1024 SPUs, 64 Texture Address Units, and 32 ROPs.

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

Theoretically, the Radeon HD 7850 should be much faster than the GeForce GT 420 overall. (explain)

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

Texel Rate

The Radeon HD 7850 is quite a bit (about 883%) more effective at AF than the GeForce GT 420. (explain)

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

Pixel Rate

The Radeon HD 7850 should be quite a bit (approximately 883%) more effective at full screen anti-aliasing than the GeForce GT 420, and will be capable of handling higher resolutions while still performing well. (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 data (measured in MB per second) that can be transported over the external memory interface in one second. The number is calculated by multiplying the interface width by its memory clock speed. In the case of DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are processed in one 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 applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate also depends on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.