Radeon HD 4870 1GB vs Radeon HD 7990

Intro

Compare those specifications to the Radeon HD 7990, which uses a 28 nm design. AMD has set the core speed at 950 MHz. The GDDR5 RAM runs at a frequency of 1500 MHz on this model. It features 2048 SPUs along with 128 Texture Address Units and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 1GB		150 Watts
Radeon HD 7990		375 Watts
	Difference: 225 Watts (150%)

Memory Bandwidth

In theory, the Radeon HD 7990 should be much faster than the Radeon HD 4870 1GB overall. (explain)

Radeon HD 7990		576000 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 460800 (400%)

Texel Rate

The Radeon HD 7990 is much (about 711%) more effective at texture filtering than the Radeon HD 4870 1GB. (explain)

Radeon HD 7990		243200 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 213200 (711%)

Pixel Rate

The Radeon HD 7990 is quite a bit (about 407%) more effective at full screen anti-aliasing than the Radeon HD 4870 1GB, and will be capable of handling higher screen resolutions without slowing down too much. (explain)

Radeon HD 7990		60800 Mpixels/sec
Radeon HD 4870 1GB		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: Bandwidth is the max amount of information (counted in megabytes per second) that can be transported across the external memory interface within a second. It's worked out by multiplying the bus width by its memory clock speed. If it uses DDR type memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. 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 amount of texture map elements (texels) that can be applied in one second. This is worked out by multiplying the total number of texture units of the card by the core clock speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum number of pixels the video card can possibly record to its local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the maximum fill rate.