Radeon HD 4870 2GB vs Radeon HD 6790

Intro

Compare that to the Radeon HD 6790, which comes with a clock speed of 840 MHz and a GDDR5 memory frequency of 1050 MHz. It also uses a 256-bit bus, and uses a 40 nm design. It features 800 SPUs, 40 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Both cards have the same power consumption.

Memory Bandwidth

The Radeon HD 6790, in theory, should perform a small bit faster than the Radeon HD 4870 2GB in general. (explain)

Radeon HD 6790		134400 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 19200 (17%)

Texel Rate

The Radeon HD 6790 will be a little bit (about 12%) more effective at AF than the Radeon HD 4870 2GB. (explain)

Radeon HD 6790		33600 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 3600 (12%)

Pixel Rate

The Radeon HD 6790 is a small bit (more or less 12%) better at full screen anti-aliasing than the Radeon HD 4870 2GB, and also will be able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 6790		13440 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 1440 (12%)

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 data (in units of megabytes per second) that can be transported past the external memory interface within a second. It's calculated by multiplying the bus width by its memory clock speed. If it uses DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

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

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly record to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of colour ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.