Radeon HD 4890 1GB vs Radeon HD 6750 1GB

Intro

Compare those specifications to the Radeon HD 6750 1GB, which has a clock frequency of 725 MHz and a GDDR5 memory frequency of 1000 MHz. It also uses a 128-bit memory bus, and uses a 40 nm design. It 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 1GB		190 Watts
	Difference: 104 Watts (121%)

Memory Bandwidth

In theory, the Radeon HD 4890 1GB should be 95% faster than the Radeon HD 6750 1GB in general, because of its greater data rate. (explain)

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

Texel Rate

The Radeon HD 4890 1GB is a lot (about 53%) more effective at anisotropic filtering than the Radeon HD 6750 1GB. (explain)

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

Pixel Rate

If running with a high resolution is important to you, then the Radeon HD 4890 1GB is the winner, and very much so. (explain)

Radeon HD 4890 1GB		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: Bandwidth is the maximum amount of data (in units of megabytes per second) that can be transferred across the external memory interface in a second. The number is calculated by multiplying the card's bus width by the speed of its memory. If the card has DDR RAM, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, HDR and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be processed per second. This figure is calculated by multiplying the total number of texture units of the card by the core speed of the chip. The better this number, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly write to the local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the the core 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 quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the maximum fill rate.