Radeon HD 7990 vs Radeon R5 M255

Intro

Compare those specifications to the Radeon R5 M255, which has a clock frequency of 940 MHz and a DDR3 memory speed of 1000 MHz. It also features a 64-bit bus, and makes use of a 28 nm design. It is comprised of 320 SPUs, 20 Texture Address Units, and 8 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

The Radeon HD 7990 should theoretically perform a lot faster than the Radeon R5 M255 overall. (explain)

Radeon HD 7990		576000 MB/sec
Radeon R5 M255		16000 MB/sec
	Difference: 560000 (3500%)

Texel Rate

The Radeon HD 7990 is a lot (about 1194%) more effective at texture filtering than the Radeon R5 M255. (explain)

Radeon HD 7990		243200 Mtexels/sec
Radeon R5 M255		18800 Mtexels/sec
	Difference: 224400 (1194%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 7990 is the winner, by far. (explain)

Radeon HD 7990		60800 Mpixels/sec
Radeon R5 M255		7520 Mpixels/sec
	Difference: 53280 (709%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the maximum amount of data (measured in megabytes per second) that can be transferred across the external memory interface in a second. It is calculated by multiplying the bus width by its memory speed. If the card has DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This figure is calculated by multiplying the total texture units by the core clock speed of the chip. The better the texel rate, the better the 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 maximum number of pixels the video card can possibly write to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of Raster Operations Pipelines 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 output rate also depends on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.