Radeon HD 4650 1GB vs Radeon R5 M255

Intro

Compare those specifications to the Radeon R5 M255, which comes with GPU clock speed of 940 MHz, and 2048 MB of DDR3 RAM set to run at 1000 MHz through a 64-bit bus. It also is comprised of 320 SPUs, 20 Texture Address Units, and 8 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

In theory, the Radeon HD 4650 1GB will be 40% faster than the Radeon R5 M255 overall, due to its greater bandwidth. (explain)

Radeon HD 4650 1GB		22400 MB/sec
Radeon R5 M255		16000 MB/sec
	Difference: 6400 (40%)

Texel Rate

The Radeon HD 4650 1GB is just a bit (approximately 2%) more effective at texture filtering than the Radeon R5 M255. (explain)

Radeon HD 4650 1GB		19200 Mtexels/sec
Radeon R5 M255		18800 Mtexels/sec
	Difference: 400 (2%)

Pixel Rate

If using a high resolution is important to you, then the Radeon R5 M255 is superior to the Radeon HD 4650 1GB, and very much so. (explain)

Radeon R5 M255		7520 Mpixels/sec
Radeon HD 4650 1GB		4800 Mpixels/sec
	Difference: 2720 (57%)

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 maximum amount of data (measured in MB per second) that can be transferred past the external memory interface in one second. It's worked out by multiplying the bus width by its memory speed. If the card has DDR RAM, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the memory bandwidth, 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 amount of texture map elements (texels) that can be processed in one second. This number is worked out by multiplying the total texture units by the core speed of the chip. The better this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

Pixel Rate: Pixel rate is the most pixels the graphics card can possibly record to the local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the amount of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. 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 ability to reach the max fill rate.