Radeon HD 4890 1GB vs Radeon HD 7790

Intro

Compare all of that to the Radeon HD 7790, which features a clock speed of 1000 MHz and a GDDR5 memory frequency 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 TAUs, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7790		85 Watts
Radeon HD 4890 1GB		190 Watts
	Difference: 105 Watts (124%)

Memory Bandwidth

Performance-wise, the Radeon HD 4890 1GB should in theory be quite a bit better than the Radeon HD 7790 overall. (explain)

Radeon HD 4890 1GB		124800 MB/sec
Radeon HD 7790		96000 MB/sec
	Difference: 28800 (30%)

Texel Rate

The Radeon HD 7790 will be quite a bit (more or less 40%) better at texture filtering than the Radeon HD 4890 1GB. (explain)

Radeon HD 7790		56000 Mtexels/sec
Radeon HD 4890 1GB		40000 Mtexels/sec
	Difference: 16000 (40%)

Pixel Rate

Both cards have the exact same pixel fill rate, so in theory they should be equally good at at FSAA, and be able to handle the same screen 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: Memory bandwidth is the maximum amount of information (counted in megabytes per second) that can be moved over the external memory interface within a second. It's worked out by multiplying the card's bus width by its memory clock speed. If the card has DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the memory bandwidth, 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 number of texture map elements (texels) that can be processed per second. This number is calculated by multiplying the total number of texture units of the card by the core clock speed of the chip. The higher this number, the better the graphics card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed per second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip can possibly write to its local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the clock speed of the card. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate is also dependant on lots of other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.