Radeon HD 4870 1GB vs Radeon HD 7850

Intro

Compare those specifications to the Radeon HD 7850, which makes use of a 28 nm design. AMD has set the core speed at 860 MHz. The GDDR5 RAM is set to run at a speed of 1200 MHz on this card. It features 1024 SPUs along with 64 Texture Address Units 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 1GB		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 1GB overall. (explain)

Radeon HD 7850		153600 MB/sec
Radeon HD 4870 1GB		115200 MB/sec
	Difference: 38400 (33%)

Texel Rate

The Radeon HD 7850 should be much (about 83%) more effective at AF than the Radeon HD 4870 1GB. (explain)

Radeon HD 7850		55040 Mtexels/sec
Radeon HD 4870 1GB		30000 Mtexels/sec
	Difference: 25040 (83%)

Pixel Rate

If running with high levels of AA is important to you, then the Radeon HD 7850 is a better choice, and very much so. (explain)

Radeon HD 7850		27520 Mpixels/sec
Radeon HD 4870 1GB		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 data (measured in megabytes per second) that can be transferred past the external memory interface in a second. It is worked out by multiplying the card's interface width by its memory clock speed. In the case of DDR memory, it should be multiplied by 2 once again. If it uses DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum number of texture map elements (texels) that are applied in one second. This 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 video card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied in one second.

Pixel Rate: Pixel rate is the maximum number of pixels that the graphics card can possibly record to the local memory per second - measured in millions of pixels per second. The number is calculated by multiplying the number of Render Output Units by the the card's clock speed. 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 rate is also dependant on lots of other factors, especially the memory bandwidth - the lower the bandwidth is, the lower the ability to get to the max fill rate.