Radeon HD 4870 2GB vs Radeon HD 7990

Intro

Compare all that to the Radeon HD 7990, which has a clock frequency of 950 MHz and a GDDR5 memory frequency of 1500 MHz. It also makes use of a 384-bit bus, and makes use of a 28 nm design. It features 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

Performance-wise, the Radeon HD 7990 should in theory be quite a bit better than the Radeon HD 4870 2GB in general. (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 a lot (about 711%) more effective at anisotropic filtering 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 a high screen resolution is important to you, then the Radeon HD 7990 is superior to the Radeon HD 4870 2GB, and very much so. (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 transferred over the external memory interface within a second. It is worked out by multiplying the card's bus width by its memory clock speed. If it uses DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are processed per second. This is calculated by multiplying the total number of texture units by the core clock 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 applied per second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly write to its local memory in one second - measured in millions of pixels per second. Pixel rate is worked out 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 outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on quite a few other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.