Radeon HD 4890 2GB vs Radeon HD 7870

Intro

Compare all that to the Radeon HD 7870, which uses a 28 nm design. AMD has set the core speed at 1000 MHz. The GDDR5 RAM runs at a frequency of 1200 MHz on this model. It features 1280 SPUs as well as 80 Texture Address Units and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7870		175 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 15 Watts (9%)

Memory Bandwidth

In theory, the Radeon HD 7870 should be 23% quicker than the Radeon HD 4890 2GB overall, because of its greater bandwidth. (explain)

Radeon HD 7870		153600 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 28800 (23%)

Texel Rate

The Radeon HD 7870 will be quite a bit (more or less 100%) better at texture filtering than the Radeon HD 4890 2GB. (explain)

Radeon HD 7870		80000 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 40000 (100%)

Pixel Rate

The Radeon HD 7870 is a lot (about 100%) better at FSAA than the Radeon HD 4890 2GB, and also capable of handling higher resolutions without losing too much performance. (explain)

Radeon HD 7870		32000 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 16000 (100%)

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.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the max amount of information (counted in megabytes per second) that can be moved past the external memory interface in a second. It is calculated by multiplying the interface width by its memory speed. In the case of DDR type memory, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that can be processed in one second. This is worked out by multiplying the total number of texture units by the core clock speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly record to the local memory in a 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 rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.