Radeon HD 4890 1GB vs Radeon HD 6770 1GB

Intro

Compare all of that to the Radeon HD 6770 1GB, which has a clock frequency of 900 MHz and a GDDR5 memory frequency of 1050 MHz. It also features a 128-bit memory bus, and makes use of a 40 nm design. It 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 1GB		190 Watts
	Difference: 82 Watts (76%)

Memory Bandwidth

The Radeon HD 4890 1GB, in theory, should be much faster than the Radeon HD 6770 1GB in general. (explain)

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

Texel Rate

The Radeon HD 4890 1GB will be a bit (approximately 11%) more effective at texture filtering than the Radeon HD 6770 1GB. (explain)

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

Pixel Rate

The Radeon HD 4890 1GB should be just a bit (approximately 11%) faster with regards to FSAA than the Radeon HD 6770 1GB, and should be capable of handling higher screen resolutions without losing too much performance. (explain)

Radeon HD 4890 1GB		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 maximum amount of data (counted in megabytes per second) that can be transferred across the external memory interface within a second. It's calculated by multiplying the card's interface width by its memory clock speed. If it uses DDR type RAM, the result should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

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

Pixel Rate: Pixel rate is the most pixels the video card can 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 Raster Operations Pipelines by the the core clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on many other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the potential to get to the max fill rate.