GeForce GT 420 vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which comes with core clock speeds of 900 MHz on the GPU, and 1782 MHz on the 2048 MB of DDR3 RAM. It features 384 SPUs as well as 32 TAUs and 16 Rasterization Operator Units.

Display Graphs

Hide Graphs

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce GT 420		50 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 15 Watts (30%)

Memory Bandwidth

Theoretically speaking, the GeForce GT 640 DDR3 will be 98% quicker than the GeForce GT 420 in general, because of its higher bandwidth. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce GT 420		28800 MB/sec
	Difference: 28224 (98%)

Texel Rate

The GeForce GT 640 DDR3 should be quite a bit (about 414%) better at anisotropic filtering than the GeForce GT 420. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce GT 420		5600 Mtexels/sec
	Difference: 23200 (414%)

Pixel Rate

If running with a high resolution is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce GT 420, by far. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce GT 420		2800 Mpixels/sec
	Difference: 11600 (414%)

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 max amount of information (measured in MB per second) that can be transferred over the external memory interface within a second. It's worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics chip can possibly write to its local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the amount of ROPs 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 also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.