Radeon HD 4870 2GB vs Radeon HD 6750 1GB

Intro

Compare that to the Radeon HD 6750 1GB, which features a clock speed of 725 MHz and a GDDR5 memory frequency of 1000 MHz. It also uses a 128-bit memory bus, and makes use of a 40 nm design. It is made up of 720 SPUs, 36 Texture Address Units, and 16 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6750 1GB		86 Watts
Radeon HD 4870 2GB		150 Watts
	Difference: 64 Watts (74%)

Memory Bandwidth

The Radeon HD 4870 2GB should theoretically perform quite a bit faster than the Radeon HD 6750 1GB overall. (explain)

Radeon HD 4870 2GB		115200 MB/sec
Radeon HD 6750 1GB		64000 MB/sec
	Difference: 51200 (80%)

Texel Rate

The Radeon HD 4870 2GB should be a bit (about 15%) faster with regards to anisotropic filtering than the Radeon HD 6750 1GB. (explain)

Radeon HD 4870 2GB		30000 Mtexels/sec
Radeon HD 6750 1GB		26100 Mtexels/sec
	Difference: 3900 (15%)

Pixel Rate

The Radeon HD 4870 2GB is a small bit (more or less 3%) more effective at anti-aliasing than the Radeon HD 6750 1GB, and also able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 4870 2GB		12000 Mpixels/sec
Radeon HD 6750 1GB		11600 Mpixels/sec
	Difference: 400 (3%)

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 maximum amount of information (measured in MB per second) that can be moved across the external memory interface within a second. The number is worked out by multiplying the card's bus width by its memory clock speed. In the case of DDR type memory, it must be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one second. This figure is calculated by multiplying the total amount of texture units 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 a second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics chip could possibly write to the local memory in one second - measured in millions of pixels per second. The number is calculated by multiplying the amount of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on many other factors, most notably the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.