GeForce GT 420 vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which has a core clock speed of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also makes use of a 128-bit memory bus, and uses a 28 nm design. It is made up of 384 SPUs, 32 TAUs, and 16 Raster Operation 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 should be 98% faster than the GeForce GT 420 in general, due to its higher data rate. (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 much (more or less 414%) faster with regards to 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

The GeForce GT 640 DDR3 is much (more or less 414%) more effective at full screen anti-aliasing than the GeForce GT 420, and also able to handle higher screen resolutions without losing too much performance. (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 maximum amount of information (measured in MB per second) that can be transported across the external memory interface in one second. The number is calculated by multiplying the card's interface width by its memory speed. In the case of DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the memory bandwidth, 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 number of texture map elements (texels) that are applied in one second. This number is worked out by multiplying the total texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per 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 calculated by multiplying the amount of ROPs by the the card's clock speed. 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 is also dependant on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.