Radeon HD 4870 2GB vs Radeon HD 7850

Intro

Compare all of that to the Radeon HD 7850, which features GPU core speed of 860 MHz, and 2048 MB of GDDR5 memory set to run at 1200 MHz through a 256-bit bus. It also is comprised of 1024 SPUs, 64 TAUs, and 32 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7850		130 Watts
Radeon HD 4870 2GB		150 Watts
	Difference: 20 Watts (15%)

Memory Bandwidth

As far as performance goes, the Radeon HD 7850 should in theory be quite a bit superior to the Radeon HD 4870 2GB in general. (explain)

Radeon HD 7850		153600 MB/sec
Radeon HD 4870 2GB		115200 MB/sec
	Difference: 38400 (33%)

Texel Rate

The Radeon HD 7850 should be quite a bit (approximately 83%) better at AF than the Radeon HD 4870 2GB. (explain)

Radeon HD 7850		55040 Mtexels/sec
Radeon HD 4870 2GB		30000 Mtexels/sec
	Difference: 25040 (83%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 7850 is superior to the Radeon HD 4870 2GB, by far. (explain)

Radeon HD 7850		27520 Mpixels/sec
Radeon HD 4870 2GB		12000 Mpixels/sec
	Difference: 15520 (129%)

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 (counted in megabytes per second) that can be transported across the external memory interface within a second. It is calculated by multiplying the bus width by its memory clock speed. If it uses DDR type RAM, it should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the memory bandwidth, the better the card will be in general. It especially helps with AA, HDR and high resolutions.

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

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