Radeon HD 4870 X2 vs Radeon HD 7870 XT

Intro

Compare all that to the Radeon HD 7870 XT, which uses a 28 nm design. AMD has set the core frequency at 925 MHz. The GDDR5 memory is set to run at a frequency of 1500 MHz on this specific model. It features 1536 SPUs along with 96 Texture Address Units and 32 ROPs.

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, because of its higher 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 is a lot (approximately 48%) better at AF 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 should be quite a bit (about 23%) faster with regards to full screen anti-aliasing than the Radeon HD 4870 X2, and also capable of handling 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 max amount of data (in units of MB per second) that can be moved over the external memory interface within a second. It's worked out by multiplying the bus width by its memory speed. If the card has DDR memory, the result should be multiplied by 2 once again. If DDR5, multiply by 4 instead. The higher the bandwidth is, the better the card will be in general. It especially helps with AA, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that are applied 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 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 that the graphics chip can possibly write to the local memory per second - measured in millions of pixels per second. Pixel rate is calculated by multiplying the amount of colour 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 is also dependant on many other factors, especially the memory bandwidth of the card - the lower the memory bandwidth is, the lower the potential to reach the maximum fill rate.