Radeon HD 4870 2GB vs Radeon HD 6770

Intro

Compare that to the Radeon HD 6770, which features GPU clock speed of 900 MHz, and 512 MB of GDDR5 memory running at 1050 MHz through a 128-bit bus. It also is comprised of 800 Stream Processors, 40 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6770		108 Watts
Radeon HD 4870 2GB		150 Watts
	Difference: 42 Watts (39%)

Memory Bandwidth

As far as performance goes, the Radeon HD 4870 2GB should theoretically be quite a bit superior to the Radeon HD 6770 in general. (explain)

Radeon HD 4870 2GB		115200 MB/sec
Radeon HD 6770		67200 MB/sec
	Difference: 48000 (71%)

Texel Rate

The Radeon HD 6770 should be a bit (about 20%) more effective at texture filtering than the Radeon HD 4870 2GB. (explain)

Radeon HD 6770		36000 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 6000 (20%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 6770 is a better choice, but only just. (explain)

Radeon HD 6770		14400 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 2400 (20%)

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 max amount of information (in units of MB per second) that can be moved across the external memory interface in one second. It's calculated by multiplying the interface width by the speed of its memory. In the case of DDR memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that can be applied per second. This is calculated by multiplying the total texture units by the core speed of the chip. The better this number, the better the video card will be at handling 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 the video card can possibly record to the local memory in a second - measured in millions of pixels per second. The number is calculated by multiplying the amount 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 outputting the pixels (image) to the screen. The actual pixel output rate also depends on quite a few other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to reach the max fill rate.