Radeon HD 4870 2GB vs Radeon HD 7990

Intro

Compare all that to the Radeon HD 7990, which has a GPU core clock speed of 950 MHz, and 3072 MB of GDDR5 memory set to run at 1500 MHz through a 384-bit bus. It also is made up of 2048 SPUs, 128 TAUs, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 2GB		150 Watts
Radeon HD 7990		375 Watts
	Difference: 225 Watts (150%)

Memory Bandwidth

In theory, the Radeon HD 7990 will be 400% faster than the Radeon HD 4870 2GB in general, because of its higher bandwidth. (explain)

Radeon HD 7990		576000 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 460800 (400%)

Texel Rate

The Radeon HD 7990 should be much (about 711%) more effective at AF than the Radeon HD 4870 2GB. (explain)

Radeon HD 7990		243200 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 213200 (711%)

Pixel Rate

If using high levels of AA 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 4870 2GB		12000 Mpixels/sec
	Difference: 48800 (407%)

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 (measured in megabytes per second) that can be moved past the external memory interface within a second. It is calculated by multiplying the bus width by its memory clock speed. In the case of DDR type memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better 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 number of texture map elements (texels) that can be processed in one second. This number is calculated by multiplying the total amount of texture units of the card by the core speed of the chip. The higher the texel rate, the better the graphics 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 could possibly record to its local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.