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GeForce 820M vs GeForce 840M

Intro

The GeForce 820M features a GPU clock speed of 719 MHz, and the 2048 MB of DDR3 memory runs at 1000 MHz through a 64-bit bus. It also features 96 SPUs, 16 Texture Address Units, and 4 ROPs.

Compare those specs to the GeForce 840M, which has GPU core speed of 1029 MHz, and 2048 MB of DDR3 memory set to run at 1000 MHz through a 64-bit bus. It also is comprised of 384 SPUs, 24 Texture Address Units, and 8 ROPs.

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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 bandwidth, so in theory they should have identical performance. (explain)

Texel Rate

The GeForce 840M will be a lot (about 115%) better at AF than the GeForce 820M. (explain)

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

Pixel Rate

If running with a high resolution is important to you, then the GeForce 840M is superior to the GeForce 820M, by far. (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

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GeForce 820M

Amazon.com

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GeForce 840M

Amazon.com

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Please note that the price comparisons are based on search keywords - sometimes it might show cards with very similar names that are not exactly the same as the one chosen in the comparison. We do try to filter out the wrong results as best we can, though.

Specifications

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Model	GeForce 820M	GeForce 840M
Manufacturer	nVidia	nVidia
Year	February 2014	March 12 2014
Code Name	GF117	GM108
Memory	2048 MB	2048 MB
Core Speed	719 MHz	1029 MHz
Memory Speed	2000 MHz	2000 MHz
Power (Max TDP)	15 watts	30 watts
Bandwidth	16000 MB/sec	16000 MB/sec
Texel Rate	11504 Mtexels/sec	24696 Mtexels/sec
Pixel Rate	2876 Mpixels/sec	8232 Mpixels/sec
Unified Shaders	96	384
Texture Mapping Units	16	24
Render Output Units	4	8
Bus Type	DDR3	DDR3
Bus Width	64-bit	64-bit
Fab Process	28 nm	28 nm
Transistors	(Unknown) million	(Unknown) million
Bus	PCIe 2.0 x16	PCIe 3.0 x16
DirectX Version	DirectX 12	DirectX 12
OpenGL Version	OpenGL 4.5	OpenGL 4.5

Memory Bandwidth: Memory bandwidth is the max amount of information (measured in megabytes per second) that can be moved over the external memory interface within a second. It's worked out by multiplying the card's interface width by its memory speed. In the case of DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

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

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly write to the local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the number of Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the max fill rate.

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