Radeon HD 4890 2GB vs Radeon HD 6750 1GB

Intro

Compare those specifications to the Radeon HD 6750 1GB, which features a GPU core clock speed of 725 MHz, and 1024 MB of GDDR5 memory running at 1000 MHz through a 128-bit bus. It also is comprised of 720 SPUs, 36 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6750 1GB		86 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 104 Watts (121%)

Memory Bandwidth

The Radeon HD 4890 2GB, in theory, should perform much faster than the Radeon HD 6750 1GB in general. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 6750 1GB		64000 MB/sec
	Difference: 60800 (95%)

Texel Rate

The Radeon HD 4890 2GB should be much (more or less 53%) better at AF than the Radeon HD 6750 1GB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 6750 1GB		26100 Mtexels/sec
	Difference: 13900 (53%)

Pixel Rate

The Radeon HD 4890 2GB will be much (approximately 38%) better at full screen anti-aliasing than the Radeon HD 6750 1GB, and also will be able to handle higher screen resolutions more effectively. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 6750 1GB		11600 Mpixels/sec
	Difference: 4400 (38%)

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 transported across the external memory interface in one second. It is calculated by multiplying the bus width by its memory clock speed. If the card has DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher the bandwidth is, 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 texture map elements (texels) that are processed in one second. This number is worked out by multiplying the total texture units of the card by the core speed of the chip. The higher this number, the better the video 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 maximum number of pixels the graphics card could possibly record to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number of colour ROPs by the clock speed of the card. ROPs (Raster Operations Pipelines - sometimes also referred to as Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.