GeForce 825M vs GeForce 840M

Intro

Compare those specifications to the GeForce 840M, which makes use of a 28 nm design. nVidia has set the core frequency at 1029 MHz. The DDR3 RAM works at a speed of 1000 MHz on this card. It features 384 SPUs as well as 24 TAUs and 8 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 840M		30 Watts
GeForce 825M		33 Watts
	Difference: 3 Watts (10%)

Memory Bandwidth

In theory, the GeForce 840M should be 11% faster than the GeForce 825M in general, because of its higher data rate. (explain)

GeForce 840M		16000 MB/sec
GeForce 825M		14400 MB/sec
	Difference: 1600 (11%)

Texel Rate

The GeForce 840M will be much (about 82%) better at AF than the GeForce 825M. (explain)

GeForce 840M		24696 Mtexels/sec
GeForce 825M		13600 Mtexels/sec
	Difference: 11096 (82%)

Pixel Rate

If using a high screen resolution is important to you, then the GeForce 840M is a better choice, and very much so. (explain)

GeForce 840M		8232 Mpixels/sec
GeForce 825M		6800 Mpixels/sec
	Difference: 1432 (21%)

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 largest amount of information (counted in megabytes per second) that can be moved past the external memory interface within a second. It is calculated by multiplying the bus width by the speed of its memory. In the case of DDR RAM, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better 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 of the card by the core clock speed of the chip. The higher this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.