Radeon HD 4850 X2 1GB vs Radeon HD 7990

Intro

Compare those specifications to the Radeon HD 7990, which features a clock speed of 950 MHz and a GDDR5 memory speed of 1500 MHz. It also uses a 384-bit bus, and uses a 28 nm design. It is comprised of 2048 SPUs, 128 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4850 X2 1GB		250 Watts
Radeon HD 7990		375 Watts
	Difference: 125 Watts (50%)

Memory Bandwidth

Theoretically, the Radeon HD 7990 should be quite a bit faster than the Radeon HD 4850 X2 1GB in general. (explain)

Radeon HD 7990		576000 MB/sec
Radeon HD 4850 X2 1GB		127104 MB/sec
	Difference: 448896 (353%)

Texel Rate

The Radeon HD 7990 will be much (more or less 386%) more effective at anisotropic filtering than the Radeon HD 4850 X2 1GB. (explain)

Radeon HD 7990		243200 Mtexels/sec
Radeon HD 4850 X2 1GB		50000 Mtexels/sec
	Difference: 193200 (386%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 7990 is the winner, by a large margin. (explain)

Radeon HD 7990		60800 Mpixels/sec
Radeon HD 4850 X2 1GB		20000 Mpixels/sec
	Difference: 40800 (204%)

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 max amount of information (in units of MB per second) that can be moved across the external memory interface in a second. It's worked out by multiplying the card's interface width by its memory clock speed. If it uses DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This is calculated by multiplying the total number of texture units by the core speed of the chip. The better this number, the better the video 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 number of pixels the graphics card can possibly record to the 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 - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.