Radeon HD 4870 512MB vs Radeon R5 M255

Intro

Compare that to the Radeon R5 M255, which features GPU core speed of 940 MHz, and 2048 MB of DDR3 memory running at 1000 MHz through a 64-bit bus. It also is comprised of 320 SPUs, 20 TAUs, and 8 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically, the Radeon HD 4870 512MB should be much 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 is quite a bit (approximately 60%) faster with regards to 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

If running with a high resolution is important to you, then the Radeon HD 4870 512MB is the winner, and very much so. (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: Bandwidth is the max amount of information (measured in megabytes per second) that can be moved across the external memory interface in a second. It's calculated by multiplying the card's interface width by its memory clock speed. If the card has DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This number is worked out by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels 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 number is calculated by multiplying the amount of Render Output Units by the the card's clock speed. ROPs (Raster Operations Pipelines - also called Render Output Units) are responsible for drawing the pixels (image) on 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 potential to reach the max fill rate.