GeForce 8600 GT 512MB DDR2 vs GeForce GT 420

Intro

Compare those specs to the GeForce GT 420, which features GPU clock speed of 700 MHz, and 2048 MB of GDDR3 memory running at 900 MHz through a 128-bit bus. It also features 48 SPUs, 8 Texture Address Units, and 4 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 8600 GT 512MB DDR2		47 Watts
GeForce GT 420		50 Watts
	Difference: 3 Watts (6%)

Memory Bandwidth

In theory, the GeForce GT 420 will be 125% quicker than the GeForce 8600 GT 512MB DDR2 overall, because of its greater bandwidth. (explain)

GeForce GT 420		28800 MB/sec
GeForce 8600 GT 512MB DDR2		12800 MB/sec
	Difference: 16000 (125%)

Texel Rate

The GeForce 8600 GT 512MB DDR2 should be much (approximately 54%) better at texture filtering than the GeForce GT 420. (explain)

GeForce 8600 GT 512MB DDR2		8640 Mtexels/sec
GeForce GT 420		5600 Mtexels/sec
	Difference: 3040 (54%)

Pixel Rate

If running with a high screen resolution is important to you, then the GeForce 8600 GT 512MB DDR2 is the winner, by a large margin. (explain)

GeForce 8600 GT 512MB DDR2		4320 Mpixels/sec
GeForce GT 420		2800 Mpixels/sec
	Difference: 1520 (54%)

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 (in units of MB per second) that can be transported across the external memory interface within a second. The number is worked out by multiplying the bus width by the speed of its memory. If the card has DDR memory, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. 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 high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the video card could possibly record to the local memory per second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.