Radeon HD 4890 2GB vs Radeon HD 7790

Intro

Compare those specs to the Radeon HD 7790, which has a GPU core clock speed of 1000 MHz, and 1024 MB of GDDR5 RAM set to run at 1500 MHz through a 128-bit bus. It also features 896 SPUs, 56 TAUs, 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

Performance-wise, the Radeon HD 4890 2GB should in theory be a lot superior to the Radeon HD 7790 overall. (explain)

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

Texel Rate

The Radeon HD 7790 will be quite a bit (approximately 40%) more effective at anisotropic 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 fill rate, so theoretically they should perform equally good at at AA, and be capable of handling 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 largest amount of information (measured in megabytes per second) that can be transferred past the external memory interface within a second. The number is worked out by multiplying the bus width by the speed of its memory. If the card has DDR memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the card's memory bandwidth, 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 per second. This is calculated by multiplying the total amount of texture units by the core speed of the chip. The better this number, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the most pixels the video card can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate is also dependant on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.