Radeon HD 4890 2GB vs Radeon HD 7790

Intro

Compare that to the Radeon HD 7790, which features a clock frequency of 1000 MHz and a GDDR5 memory speed of 1500 MHz. It also makes use of a 128-bit memory bus, and uses a 28 nm design. It is made up of 896 SPUs, 56 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7790		85 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 105 Watts (124%)

Memory Bandwidth

In theory, the Radeon HD 4890 2GB should be 30% quicker than the Radeon HD 7790 overall, due to its higher data rate. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 7790		96000 MB/sec
	Difference: 28800 (30%)

Texel Rate

The Radeon HD 7790 should be a lot (more or less 40%) better at texture filtering than the Radeon HD 4890 2GB. (explain)

Radeon HD 7790		56000 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 16000 (40%)

Pixel Rate

Both cards have the exact same pixel rate, so in theory they should perform equally good at at AA, and be able to handle the same resolutions. (explain)

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 (measured in MB per second) that can be transported across the external memory interface in one second. It is worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR type RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the 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 number of texture map elements (texels) that can be processed in one second. This figure is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The better the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly record to the local memory in one second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the the core speed of the card. ROPs (Raster Operations Pipelines - also sometimes 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 of the card - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.