GeForce 820M vs GeForce 840M

Intro

Compare those specs to the GeForce 840M, which comes with a core clock speed of 1029 MHz and a DDR3 memory frequency of 1000 MHz. It also makes use of a 64-bit bus, and uses a 28 nm design. It is made up of 384 SPUs, 24 Texture Address Units, and 8 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 840M		1600 points
GeForce 820M		850 points
	Difference: 750 (88%)

Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 820M		15 Watts
GeForce 840M		30 Watts
	Difference: 15 Watts (100%)

Memory Bandwidth

Both cards have the exact same memory bandwidth, so theoretically they should have the same performance. (explain)

Texel Rate

The GeForce 840M will be a lot (about 115%) faster with regards to anisotropic filtering than the GeForce 820M. (explain)

GeForce 840M		24696 Mtexels/sec
GeForce 820M		11504 Mtexels/sec
	Difference: 13192 (115%)

Pixel Rate

The GeForce 840M should be a lot (about 186%) better at anti-aliasing than the GeForce 820M, and should be able to handle higher resolutions better. (explain)

GeForce 840M		8232 Mpixels/sec
GeForce 820M		2876 Mpixels/sec
	Difference: 5356 (186%)

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 data (counted in MB per second) that can be transported past the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR type RAM, it should be multiplied by 2 once 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 AA, 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 number is calculated by multiplying the total texture units by the core speed of the chip. The higher this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly record to the local memory per second - measured in millions of pixels per second. The number is worked out by multiplying the amount of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.