GeForce GTX 660 vs Radeon R9 M390X

Intro

Compare those specs to the Radeon R9 M390X, which comes with GPU core speed of 723 MHz, and 4096 MB of GDDR5 RAM running at 1250 MHz through a 256-bit bus. It also features 2048 SPUs, 128 Texture Address Units, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon R9 M390X		125 Watts
GeForce GTX 660		140 Watts
	Difference: 15 Watts (12%)

Memory Bandwidth

In theory, the Radeon R9 M390X should perform a small bit faster than the GeForce GTX 660 overall. (explain)

Radeon R9 M390X		160000 MB/sec
GeForce GTX 660		144192 MB/sec
	Difference: 15808 (11%)

Texel Rate

The Radeon R9 M390X should be a small bit (approximately 18%) faster with regards to AF than the GeForce GTX 660. (explain)

Radeon R9 M390X		92544 Mtexels/sec
GeForce GTX 660		78400 Mtexels/sec
	Difference: 14144 (18%)

Pixel Rate

The GeForce GTX 660 is just a bit (approximately 2%) more effective at FSAA than the Radeon R9 M390X, and also should be able to handle higher screen resolutions more effectively. (explain)

GeForce GTX 660		23520 Mpixels/sec
Radeon R9 M390X		23136 Mpixels/sec
	Difference: 384 (2%)

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 information (counted in MB per second) that can be transported across the external memory interface in one second. The number is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR type RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied per second. This figure is calculated by multiplying the total texture units of the card by the core clock 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 applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly record to its local memory in a second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. 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, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to get to the maximum fill rate.