Radeon HD 4790 vs Radeon HD 7870

Intro

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

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

As far as performance goes, the Radeon HD 7870 should in theory be a lot better than the Radeon HD 4790 overall. (explain)

Radeon HD 7870		153600 MB/sec
Radeon HD 4790		102400 MB/sec
	Difference: 51200 (50%)

Texel Rate

The Radeon HD 7870 will be a lot (approximately 317%) more effective at AF than the Radeon HD 4790. (explain)

Radeon HD 7870		80000 Mtexels/sec
Radeon HD 4790		19200 Mtexels/sec
	Difference: 60800 (317%)

Pixel Rate

The Radeon HD 7870 will be a lot (more or less 233%) more effective at AA than the Radeon HD 4790, and will be able to handle higher screen resolutions while still performing well. (explain)

Radeon HD 7870		32000 Mpixels/sec
Radeon HD 4790		9600 Mpixels/sec
	Difference: 22400 (233%)

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: Memory bandwidth is the largest amount of information (in units of megabytes per second) that can be transferred over the external memory interface within a second. It's worked out by multiplying the interface width by its memory clock speed. In the case of DDR RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, 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 better this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a 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 Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the maximum fill rate.