Radeon HD 4890 2GB vs Radeon HD 6770 1GB

Intro

Compare those specs to the Radeon HD 6770 1GB, which features GPU clock speed of 900 MHz, and 1024 MB of GDDR5 RAM set to run at 1050 MHz through a 128-bit bus. It also is comprised of 800 SPUs, 40 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6770 1GB		108 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 82 Watts (76%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4890 2GB will be 86% faster than the Radeon HD 6770 1GB overall, because of its greater bandwidth. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 6770 1GB		67200 MB/sec
	Difference: 57600 (86%)

Texel Rate

The Radeon HD 4890 2GB is a bit (about 11%) better at texture filtering than the Radeon HD 6770 1GB. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 6770 1GB		36000 Mtexels/sec
	Difference: 4000 (11%)

Pixel Rate

The Radeon HD 4890 2GB should be a bit (more or less 11%) better at anti-aliasing than the Radeon HD 6770 1GB, and also able to handle higher resolutions without slowing down too much. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 6770 1GB		14400 Mpixels/sec
	Difference: 1600 (11%)

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 (in units of megabytes per second) that can be transported across the external memory interface in a second. The number is calculated by multiplying the card's interface width by its memory clock speed. In the case of DDR type memory, it must be multiplied by 2 once again. If it uses DDR5, multiply by ANOTHER 2x. The higher the card's memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR 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 number of texture units of the card by the core clock speed of the chip. The higher the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in a second.

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