GeForce 820M vs Radeon HD 4870 X2

Intro

Compare those specs to the Radeon HD 4870 X2, which uses a 55 nm design. AMD has clocked the core frequency at 750 MHz. The GDDR5 RAM is set to run at a speed of 900 MHz on this model. It features 800(160x5) SPUs along with 40 TAUs and 16 ROPs.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

GeForce 820M		15 Watts
Radeon HD 4870 X2		350 Watts
	Difference: 335 Watts (2233%)

Memory Bandwidth

The Radeon HD 4870 X2 should theoretically be a lot faster than the GeForce 820M overall. (explain)

Radeon HD 4870 X2		230400 MB/sec
GeForce 820M		16000 MB/sec
	Difference: 214400 (1340%)

Texel Rate

The Radeon HD 4870 X2 is quite a bit (about 422%) faster with regards to anisotropic filtering than the GeForce 820M. (explain)

Radeon HD 4870 X2		60000 Mtexels/sec
GeForce 820M		11504 Mtexels/sec
	Difference: 48496 (422%)

Pixel Rate

The Radeon HD 4870 X2 will be quite a bit (approximately 734%) more effective at FSAA than the GeForce 820M, and will be able to handle higher screen resolutions without slowing down too much. (explain)

Radeon HD 4870 X2		24000 Mpixels/sec
GeForce 820M		2876 Mpixels/sec
	Difference: 21124 (734%)

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 maximum amount of data (measured in MB per second) that can be transported past the external memory interface within a second. It is calculated by multiplying the interface width by its memory speed. In the case of DDR memory, it should be multiplied by 2 again. If it uses DDR5, multiply by ANOTHER 2x. The better the card's memory bandwidth, the faster the card will be in general. It especially helps with AA, High Dynamic Range and higher screen resolutions.

Texel Rate: Texel rate is the maximum texture map elements (texels) that are applied in one second. This is calculated by multiplying the total amount of texture units of the card by the core clock speed of the chip. The higher this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels processed in one second.

Pixel Rate: Pixel rate is the most pixels that the graphics card could possibly record to the local memory in one second - measured in millions of pixels per second. The number is worked out by multiplying the number of ROPs by the the core speed of the card. ROPs (Raster Operations Pipelines - aka Render Output Units) are responsible for drawing the pixels (image) on the screen. The actual pixel fill rate also depends on lots of other factors, especially the memory bandwidth of the card - the lower the bandwidth is, the lower the ability to get to the maximum fill rate.