GeForce 840M vs GeForce 9400 GT 256MB

Intro

Compare those specifications to the GeForce 9400 GT 256MB, which comes with GPU core speed of 550 MHz, and 256 MB of GDDR2 RAM set to run at 400 MHz through a 128-bit bus. It also is comprised of 16 Stream Processors, 8 Texture Address Units, and 4 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 840M		30 Watts
GeForce 9400 GT 256MB		50 Watts
	Difference: 20 Watts (67%)

Memory Bandwidth

The GeForce 840M, in theory, should be much faster than the GeForce 9400 GT 256MB overall. (explain)

GeForce 840M		16000 MB/sec
GeForce 9400 GT 256MB		12800 MB/sec
	Difference: 3200 (25%)

Texel Rate

The GeForce 840M will be a lot (about 461%) more effective at texture filtering than the GeForce 9400 GT 256MB. (explain)

GeForce 840M		24696 Mtexels/sec
GeForce 9400 GT 256MB		4400 Mtexels/sec
	Difference: 20296 (461%)

Pixel Rate

The GeForce 840M should be a lot (about 274%) faster with regards to AA than the GeForce 9400 GT 256MB, and should be able to handle higher resolutions more effectively. (explain)

GeForce 840M		8232 Mpixels/sec
GeForce 9400 GT 256MB		2200 Mpixels/sec
	Difference: 6032 (274%)

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 information (counted in MB per second) that can be transported past the external memory interface within a second. The number is calculated by multiplying the bus width by its memory speed. If it uses DDR RAM, the result should be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The better the card's 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 texture map elements (texels) that are processed in one second. This is calculated by multiplying the total number of texture units by the core speed of the chip. The higher this number, the better the graphics 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 can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of 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 fill rate is also dependant on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.