Radeon HD 3870 X2 512MB vs Radeon HD 4850 512MB

Intro

Compare those specifications to the Radeon HD 4850 512MB, which comes with a core clock speed of 625 MHz and a GDDR3 memory speed of 993 MHz. It also uses a 256-bit memory bus, and uses a 55 nm design. It is comprised of 800(160x5) SPUs, 40 Texture Address Units, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Memory Bandwidth

Theoretically speaking, the Radeon HD 3870 X2 512MB is 81% faster than the Radeon HD 4850 512MB overall, because of its higher data rate. (explain)

Radeon HD 3870 X2 512MB		115200 MB/sec
Radeon HD 4850 512MB		63552 MB/sec
	Difference: 51648 (81%)

Texel Rate

The Radeon HD 3870 X2 512MB should be a small bit (approximately 6%) more effective at anisotropic filtering than the Radeon HD 4850 512MB. (explain)

Radeon HD 3870 X2 512MB		26400 Mtexels/sec
Radeon HD 4850 512MB		25000 Mtexels/sec
	Difference: 1400 (6%)

Pixel Rate

The Radeon HD 3870 X2 512MB will be much (about 164%) faster with regards to anti-aliasing than the Radeon HD 4850 512MB, and capable of handling higher resolutions while still performing well. (explain)

Radeon HD 3870 X2 512MB		26400 Mpixels/sec
Radeon HD 4850 512MB		10000 Mpixels/sec
	Difference: 16400 (164%)

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: Memory bandwidth is the largest amount of information (measured in MB per second) that can be transferred past the external memory interface in a second. It's worked out by multiplying the bus width by its memory speed. In the case of DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by 4 instead. The better the bandwidth is, 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 are processed in one second. This number is worked out by multiplying the total number of texture units of the card by the core speed of the chip. The higher the texel rate, the better the 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 amount of pixels the graphics card can possibly record to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of Raster Operations Pipelines by the the card's clock speed. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.