GeForce 8400 GS 512MB vs GeForce GT 420

Intro

Compare those specs to the GeForce GT 420, which comes with core clock speeds of 700 MHz on the GPU, and 900 MHz on the 2048 MB of GDDR3 RAM. It features 48 SPUs along with 8 Texture Address Units and 4 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8400 GS 512MB		40 Watts
GeForce GT 420		50 Watts
	Difference: 10 Watts (25%)

Memory Bandwidth

The GeForce GT 420, in theory, should perform a lot faster than the GeForce 8400 GS 512MB in general. (explain)

GeForce GT 420		28800 MB/sec
GeForce 8400 GS 512MB		6400 MB/sec
	Difference: 22400 (350%)

Texel Rate

The GeForce GT 420 is a little bit (about 8%) better at AF than the GeForce 8400 GS 512MB. (explain)

GeForce GT 420		5600 Mtexels/sec
GeForce 8400 GS 512MB		5200 Mtexels/sec
	Difference: 400 (8%)

Pixel Rate

The GeForce GT 420 is a little bit (approximately 8%) better at FSAA than the GeForce 8400 GS 512MB, and also will be capable of handling higher screen resolutions without slowing down too much. (explain)

GeForce GT 420		2800 Mpixels/sec
GeForce 8400 GS 512MB		2600 Mpixels/sec
	Difference: 200 (8%)

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 (counted in MB per second) that can be transferred over the external memory interface within a second. The number is worked out by multiplying the interface width by its memory speed. If the card has DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster 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 applied 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 card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.