Radeon HD 4870 X2 vs Radeon HD 7870 XT

Intro

Compare that to the Radeon HD 7870 XT, which comes with GPU core speed of 925 MHz, and 2048 MB of GDDR5 RAM set to run at 1500 MHz through a 256-bit bus. It also is made up of 1536 Stream Processors, 96 TAUs, and 32 Raster Operation Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 7870 XT		185 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 165 Watts (89%)

Memory Bandwidth

Theoretically speaking, the Radeon HD 4870 X2 should be 20% faster than the Radeon HD 7870 XT overall, due to its greater data rate. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 7870 XT		192000 MB/sec
	Difference: 38400 (20%)

Texel Rate

The Radeon HD 7870 XT will be a lot (more or less 48%) better at anisotropic filtering than the Radeon HD 4870 X2. (explain)

Radeon HD 7870 XT		88800 Mtexels/sec
Radeon HD 4870 X2		60000 Mtexels/sec
	Difference: 28800 (48%)

Pixel Rate

The Radeon HD 7870 XT will be much (about 23%) faster with regards to anti-aliasing than the Radeon HD 4870 X2, and should be able to handle higher resolutions without losing too much performance. (explain)

Radeon HD 7870 XT		29600 Mpixels/sec
Radeon HD 4870 X2		24000 Mpixels/sec
	Difference: 5600 (23%)

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 maximum amount of data (in units of megabytes per second) that can be transported across the external memory interface within a second. It is calculated by multiplying the card's interface width by its memory speed. If the card has DDR type RAM, the result should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The higher the memory bandwidth, the better the card will be in general. It especially helps with anti-aliasing, HDR and high resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are processed per second. This is worked out by multiplying the total amount of texture units by the core speed of the chip. The better this number, the better the graphics card will be at texture filtering (anisotropic filtering - AF). It is measured in millions of texels in a second.

Pixel Rate: Pixel rate is the maximum amount of pixels that the graphics chip could possibly record to its local memory in a second - measured in millions of pixels per second. The figure is calculated by multiplying the number of ROPs 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 rate also depends on lots of other factors, most notably the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the max fill rate.