Radeon HD 4890 1GB vs Radeon R5 M255

Intro

Compare that to the Radeon R5 M255, which makes use of a 28 nm design. AMD has set the core speed at 940 MHz. The DDR3 memory runs at a frequency of 1000 MHz on this particular model. It features 320 SPUs along with 20 Texture Address Units and 8 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 4890 1GB is 680% faster than the Radeon R5 M255 in general, because of its greater bandwidth. (explain)

Radeon HD 4890 1GB		124800 MB/sec
Radeon R5 M255		16000 MB/sec
	Difference: 108800 (680%)

Texel Rate

The Radeon HD 4890 1GB should be a lot (approximately 113%) better at anisotropic filtering than the Radeon R5 M255. (explain)

Radeon HD 4890 1GB		40000 Mtexels/sec
Radeon R5 M255		18800 Mtexels/sec
	Difference: 21200 (113%)

Pixel Rate

The Radeon HD 4890 1GB is a lot (about 113%) more effective at FSAA than the Radeon R5 M255, and will be able to handle higher resolutions better. (explain)

Radeon HD 4890 1GB		16000 Mpixels/sec
Radeon R5 M255		7520 Mpixels/sec
	Difference: 8480 (113%)

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 largest amount of information (measured in megabytes per second) that can be moved over the external memory interface in a second. It is worked out by multiplying the card's interface width by its memory speed. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The higher the bandwidth is, 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 amount of texture map elements (texels) that can be processed per second. This number is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The higher 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 that the graphics chip could possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is worked out by multiplying the amount of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on quite a few other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.