GeForce GT 420 vs Radeon HD 7790

Intro

Compare that to the Radeon HD 7790, which comes with a clock frequency of 1000 MHz and a GDDR5 memory speed of 1500 MHz. It also uses a 128-bit memory bus, and makes use of a 28 nm design. It is comprised of 896 SPUs, 56 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 7790		85 Watts
	Difference: 35 Watts (70%)

Memory Bandwidth

The Radeon HD 7790 should theoretically be quite a bit faster than the GeForce GT 420 overall. (explain)

Radeon HD 7790		96000 MB/sec
GeForce GT 420		28800 MB/sec
	Difference: 67200 (233%)

Texel Rate

The Radeon HD 7790 is a lot (more or less 900%) better at AF than the GeForce GT 420. (explain)

Radeon HD 7790		56000 Mtexels/sec
GeForce GT 420		5600 Mtexels/sec
	Difference: 50400 (900%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 7790 is a better choice, and very much so. (explain)

Radeon HD 7790		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: Memory bandwidth is the largest amount of information (in units of megabytes per second) that can be moved past the external memory interface in a second. It is calculated by multiplying the interface width by its memory speed. If it uses DDR memory, it must be multiplied by 2 again. If 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 higher screen resolutions.

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

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