Radeon HD 7990 vs Radeon RX 6800 XT

Intro

Compare those specifications to the Radeon RX 6800 XT, which has a clock frequency of 1825 MHz and a GDDR6 memory speed of 2000 MHz. It also features a 256-bit bus, and uses a 7 nm design. It is made up of 4608 SPUs, 288 Texture Address Units, and 128 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon RX 6800 XT		300 Watts
Radeon HD 7990		375 Watts
	Difference: 75 Watts (25%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 7990 will be 10% quicker than the Radeon RX 6800 XT in general, due to its higher data rate. (explain)

Radeon HD 7990		576000 MB/sec
Radeon RX 6800 XT		524288 MB/sec
	Difference: 51712 (10%)

Texel Rate

The Radeon RX 6800 XT is quite a bit (more or less 116%) faster with regards to AF than the Radeon HD 7990. (explain)

Radeon RX 6800 XT		525600 Mtexels/sec
Radeon HD 7990		243200 Mtexels/sec
	Difference: 282400 (116%)

Pixel Rate

If using a high screen resolution is important to you, then the Radeon RX 6800 XT is the winner, and very much so. (explain)

Radeon RX 6800 XT		233600 Mpixels/sec
Radeon HD 7990		60800 Mpixels/sec
	Difference: 172800 (284%)

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 (measured in MB per second) that can be transported past the external memory interface within a second. It is worked out by multiplying the card's bus width by its memory speed. In the case of DDR RAM, the result should 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 amount of texture map elements (texels) that are processed per second. This is calculated by multiplying the total number of texture units by the core 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 applied in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics card can possibly record to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number 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 rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to reach the max fill rate.