Radeon HD 7990 vs Radeon R9 M275X

Intro

Compare those specifications to the Radeon R9 M275X, which has a clock frequency of 900 MHz and a GDDR5 memory frequency of 1125 MHz. It also features a 128-bit bus, and makes use of a 28 nm design. It is comprised of 640 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon R9 M275X		50 Watts
Radeon HD 7990		375 Watts
	Difference: 325 Watts (650%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 7990 should be 700% faster than the Radeon R9 M275X in general, because of its higher bandwidth. (explain)

Radeon HD 7990		576000 MB/sec
Radeon R9 M275X		72000 MB/sec
	Difference: 504000 (700%)

Texel Rate

The Radeon HD 7990 is quite a bit (approximately 576%) better at anisotropic filtering than the Radeon R9 M275X. (explain)

Radeon HD 7990		243200 Mtexels/sec
Radeon R9 M275X		36000 Mtexels/sec
	Difference: 207200 (576%)

Pixel Rate

The Radeon HD 7990 is much (about 322%) faster with regards to full screen anti-aliasing than the Radeon R9 M275X, and capable of handling higher screen resolutions better. (explain)

Radeon HD 7990		60800 Mpixels/sec
Radeon R9 M275X		14400 Mpixels/sec
	Difference: 46400 (322%)

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 largest amount of information (counted in MB per second) that can be transported past the external memory interface within a second. It is calculated by multiplying the interface width by the speed of its memory. In the case of DDR memory, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be applied in one second. This number is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the maximum number of pixels the graphics card could possibly record to its local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the max fill rate.