Radeon HD 4890 2GB vs Radeon HD 7850

Intro

Compare that to the Radeon HD 7850, which features a clock frequency of 860 MHz and a GDDR5 memory speed of 1200 MHz. It also uses a 256-bit bus, and makes use of a 28 nm design. It is comprised of 1024 SPUs, 64 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7850		130 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 60 Watts (46%)

Memory Bandwidth

The Radeon HD 7850 should in theory be quite a bit faster than the Radeon HD 4890 2GB overall. (explain)

Radeon HD 7850		153600 MB/sec
Radeon HD 4890 2GB		124800 MB/sec
	Difference: 28800 (23%)

Texel Rate

The Radeon HD 7850 should be quite a bit (approximately 38%) better at AF than the Radeon HD 4890 2GB. (explain)

Radeon HD 7850		55040 Mtexels/sec
Radeon HD 4890 2GB		40000 Mtexels/sec
	Difference: 15040 (38%)

Pixel Rate

If running with a high screen resolution is important to you, then the Radeon HD 7850 is a better choice, by a large margin. (explain)

Radeon HD 7850		27520 Mpixels/sec
Radeon HD 4890 2GB		16000 Mpixels/sec
	Difference: 11520 (72%)

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 (counted in megabytes per second) that can be moved over the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory speed. If the card has DDR RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed in one 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 handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels the graphics card could possibly record to the local memory in a second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the number of colour ROPs by the the card's 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 also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to reach the max fill rate.