Radeon HD 4870 X2 vs Radeon HD 7850

Intro

Compare all of that to the Radeon HD 7850, which has a clock frequency of 860 MHz and a GDDR5 memory frequency of 1200 MHz. It also makes use of a 256-bit bus, and makes use of a 28 nm design. It features 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 X2		350 Watts
	Difference: 220 Watts (169%)

Memory Bandwidth

In theory, the Radeon HD 4870 X2 should be a lot faster than the Radeon HD 7850 overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 7850		153600 MB/sec
	Difference: 76800 (50%)

Texel Rate

The Radeon HD 4870 X2 should be just a bit (more or less 9%) faster with regards to texture filtering than the Radeon HD 7850. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 7850		55040 Mtexels/sec
	Difference: 4960 (9%)

Pixel Rate

The Radeon HD 7850 will be a small bit (more or less 15%) more effective at full screen anti-aliasing than the Radeon HD 4870 X2, and should be capable of handling higher resolutions more effectively. (explain)

Radeon HD 7850		27520 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 3520 (15%)

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.

One or more cards in this comparison are multi-core. This means that their bandwidth, texel and pixel rates are theoretically doubled - this does not mean the card will actually perform twice as fast, but only that it should in theory be able to. Actual game benchmarks will give a more accurate idea of what it's capable of.

Price Comparison

Specifications

Memory Bandwidth: Bandwidth is the largest amount of information (in units of megabytes per second) that can be transferred over the external memory interface in one second. The number is calculated by multiplying the bus width by its memory speed. In the case of DDR memory, it must be multiplied by 2 once again. If DDR5, multiply by 4 instead. The better the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and higher screen 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 number of texture units of the card by the core clock speed of the chip. The higher this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels applied per second.

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