GeForce 820M vs GeForce GT 640 DDR3

Intro

Compare that to the GeForce GT 640 DDR3, which comes with GPU clock speed of 900 MHz, and 2048 MB of DDR3 RAM set to run at 1782 MHz through a 128-bit bus. It also is made up of 384 SPUs, 32 TAUs, and 16 Raster Operation Units.

Display Graphs

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Benchmarks

These are real-world performance benchmarks that were submitted by Hardware Compare users. The scores seen here are the average of all benchmarks submitted for each respective test and hardware.

3DMark Fire Strike Graphics Score

GeForce GT 640 DDR3		1560 points
GeForce 820M		850 points
	Difference: 710 (84%)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 820M		15 Watts
GeForce GT 640 DDR3		65 Watts
	Difference: 50 Watts (333%)

Memory Bandwidth

Theoretically, the GeForce GT 640 DDR3 should be much faster than the GeForce 820M in general. (explain)

GeForce GT 640 DDR3		57024 MB/sec
GeForce 820M		16000 MB/sec
	Difference: 41024 (256%)

Texel Rate

The GeForce GT 640 DDR3 will be much (about 150%) faster with regards to AF than the GeForce 820M. (explain)

GeForce GT 640 DDR3		28800 Mtexels/sec
GeForce 820M		11504 Mtexels/sec
	Difference: 17296 (150%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the GeForce GT 640 DDR3 is superior to the GeForce 820M, by a large margin. (explain)

GeForce GT 640 DDR3		14400 Mpixels/sec
GeForce 820M		2876 Mpixels/sec
	Difference: 11524 (401%)

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 data (measured in megabytes per second) that can be transported across the external memory interface in a second. It's calculated by multiplying the bus width by its memory clock speed. In the case of DDR type RAM, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better 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 texture map elements (texels) that are processed in one second. This figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better this number, the better the graphics 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 maximum amount of pixels that the graphics card can possibly write to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.