Radeon HD 4870 2GB vs Radeon HD 6870

Intro

Compare all of that to the Radeon HD 6870, which has GPU core speed of 900 MHz, and 1024 MB of GDDR5 RAM running at 1050 MHz through a 256-bit bus. It also is comprised of 1120 Stream Processors, 56 Texture Address Units, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 2GB		150 Watts
Radeon HD 6870		151 Watts
	Difference: 1 Watts (1%)

Memory Bandwidth

In theory, the Radeon HD 6870 is 17% faster than the Radeon HD 4870 2GB overall, due to its higher data rate. (explain)

Radeon HD 6870		134400 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 19200 (17%)

Texel Rate

The Radeon HD 6870 is a lot (approximately 68%) more effective at AF than the Radeon HD 4870 2GB. (explain)

Radeon HD 6870		50400 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 20400 (68%)

Pixel Rate

The Radeon HD 6870 will be a lot (approximately 140%) better at full screen anti-aliasing than the Radeon HD 4870 2GB, and also capable of handling higher screen resolutions while still performing well. (explain)

Radeon HD 6870		28800 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 16800 (140%)

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 information (counted in MB per second) that can be moved across the external memory interface in one second. It's 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 ANOTHER 2x. The better the card's memory bandwidth, the faster 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 is worked out by multiplying the total amount of texture units of the card by the core speed of the chip. The higher this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the most pixels the graphics card could possibly write to its local memory in one second - measured in millions of pixels per second. The figure is calculated by multiplying the amount of colour ROPs by the the card's clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel output rate is also dependant on quite a few 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.