Radeon HD 7870 vs Radeon R9 M390X

Intro

Compare all that to the Radeon R9 M390X, which features GPU clock speed of 723 MHz, and 4096 MB of GDDR5 RAM set to run at 1250 MHz through a 256-bit bus. It also is comprised of 2048 Stream Processors, 128 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon R9 M390X		125 Watts
Radeon HD 7870		175 Watts
	Difference: 50 Watts (40%)

Memory Bandwidth

In theory, the Radeon R9 M390X should be a small bit faster than the Radeon HD 7870 overall. (explain)

Radeon R9 M390X		160000 MB/sec
Radeon HD 7870		153600 MB/sec
	Difference: 6400 (4%)

Texel Rate

The Radeon R9 M390X is a bit (about 16%) more effective at texture filtering than the Radeon HD 7870. (explain)

Radeon R9 M390X		92544 Mtexels/sec
Radeon HD 7870		80000 Mtexels/sec
	Difference: 12544 (16%)

Pixel Rate

The Radeon HD 7870 is quite a bit (approximately 38%) better at anti-aliasing than the Radeon R9 M390X, and also should be able to handle higher screen resolutions without slowing down too much. (explain)

Radeon HD 7870		32000 Mpixels/sec
Radeon R9 M390X		23136 Mpixels/sec
	Difference: 8864 (38%)

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 (measured in megabytes per second) that can be moved over the external memory interface in one second. It is calculated by multiplying the card's interface width by its memory speed. In the case of DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the better 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 processed per second. This number is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The better the texel rate, 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 amount of pixels the video card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.