GeForce 820M vs GeForce GT 640 DDR3

Intro

Compare all that to the GeForce GT 640 DDR3, which comes with a core clock speed of 900 MHz and a DDR3 memory frequency of 1782 MHz. It also uses a 128-bit memory bus, and makes use of a 28 nm design. It is comprised of 384 SPUs, 32 TAUs, and 16 ROPs.

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

As far as performance goes, the GeForce GT 640 DDR3 should theoretically be quite a bit better than the GeForce 820M overall. (explain)

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

Texel Rate

The GeForce GT 640 DDR3 should be a lot (approximately 150%) more effective at texture filtering than the GeForce 820M. (explain)

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

Pixel Rate

The GeForce GT 640 DDR3 should be a lot (about 401%) faster with regards to AA than the GeForce 820M, and should be able to handle higher screen resolutions better. (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 (in units of megabytes per second) that can be moved across the external memory interface in a second. The number is calculated by multiplying the interface width by the speed of its memory. If it uses DDR memory, the result should be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The better the 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 per second. This figure is worked out by multiplying the total amount of texture units by the core speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to its local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.