Radeon HD 4870 512MB vs Radeon HD 4870 X2

Intro

Compare that to the Radeon HD 4870 X2, which features a core clock frequency of 750 MHz and a GDDR5 memory frequency of 900 MHz. It also makes use of a 256-bit bus, and makes use of a 55 nm design. It features 800(160x5) SPUs, 40 TAUs, and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 4870 512MB		150 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 200 Watts (133%)

Memory Bandwidth

The Radeon HD 4870 X2 should in theory perform much faster than the Radeon HD 4870 512MB overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
Radeon HD 4870 512MB		115200 MB/sec
	Difference: 115200 (100%)

Texel Rate

The Radeon HD 4870 X2 is much (approximately 100%) better at AF than the Radeon HD 4870 512MB. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
Radeon HD 4870 512MB		30000 Mtexels/sec
	Difference: 30000 (100%)

Pixel Rate

The Radeon HD 4870 X2 is a lot (more or less 100%) faster with regards to FSAA than the Radeon HD 4870 512MB, and should be capable of handling higher resolutions better. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
Radeon HD 4870 512MB		12000 Mpixels/sec
	Difference: 12000 (100%)

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 (measured in MB per second) that can be transferred over the external memory interface within a second. It's calculated by multiplying the bus width by its memory clock speed. If it uses DDR memory, it should be multiplied by 2 once again. If DDR5, multiply by ANOTHER 2x. The better the memory bandwidth, the faster the card will be in general. It especially helps with anti-aliasing, High Dynamic Range and high resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied in one second. This number is worked out 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 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 maximum amount of pixels that the graphics card can possibly write to its local memory per second - measured in millions of pixels per second. The figure is worked out by multiplying the amount of ROPs by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel output rate also depends on quite a few other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the ability to get to the maximum fill rate.