Radeon HD 4870 2GB vs Radeon HD 7850

Intro

Compare that to the Radeon HD 7850, which comes with a clock frequency of 860 MHz and a GDDR5 memory speed of 1200 MHz. It also features a 256-bit bus, and uses a 28 nm design. It 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

The Radeon HD 7850, in theory, should be quite a bit faster than the Radeon HD 4870 2GB overall. (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 much (approximately 83%) faster with regards to texture filtering 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

The Radeon HD 7850 should be a lot (approximately 129%) more effective at anti-aliasing than the Radeon HD 4870 2GB, and also should be capable of handling higher screen resolutions better. (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: Memory bandwidth is the maximum amount of information (measured in MB per second) that can be moved over the external memory interface within a second. It is worked out by multiplying the card's interface width by the speed of its memory. If the card has DDR type RAM, the result should be multiplied by 2 again. If it uses DDR5, multiply by 4 instead. The higher 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 amount of texture map elements (texels) that are processed per second. This is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The better the texel rate, the better the video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in one second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly write to its local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the number of Raster Operations Pipelines by the clock speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for filling the screen with pixels (the image). The actual pixel fill rate is also dependant on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the potential to get to the max fill rate.