Radeon HD 4870 512MB vs Radeon R5 M255

Intro

Compare that to the Radeon R5 M255, which uses a 28 nm design. AMD has clocked the core frequency at 940 MHz. The DDR3 memory works at a speed of 1000 MHz on this card. It features 320 SPUs as well as 20 Texture Address Units and 8 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically, the Radeon HD 4870 512MB should be a lot faster than the Radeon R5 M255 overall. (explain)

Radeon HD 4870 512MB		115200 MB/sec
Radeon R5 M255		16000 MB/sec
	Difference: 99200 (620%)

Texel Rate

The Radeon HD 4870 512MB will be quite a bit (more or less 60%) more effective at anisotropic filtering than the Radeon R5 M255. (explain)

Radeon HD 4870 512MB		30000 Mtexels/sec
Radeon R5 M255		18800 Mtexels/sec
	Difference: 11200 (60%)

Pixel Rate

The Radeon HD 4870 512MB is quite a bit (about 60%) faster with regards to AA than the Radeon R5 M255, and will be capable of handling higher screen resolutions while still performing well. (explain)

Radeon HD 4870 512MB		12000 Mpixels/sec
Radeon R5 M255		7520 Mpixels/sec
	Difference: 4480 (60%)

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 (counted in megabytes per second) that can be transported over the external memory interface in a second. It's calculated by multiplying the interface width by its memory clock speed. In the case of DDR RAM, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the bandwidth is, the better 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 are applied per second. This figure is worked out 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 card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly record to its local memory in one second - measured in millions of pixels per second. Pixel rate is calculated 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 drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to reach the max fill rate.