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Originally Posted by phextwin
Somehow i doubt anywhere near 100W. Look at the dinky little heatsink on the x800xt. Even the 6800U/x850xt sink is much smaller than a 560P4 for instance, a well known ~100W cpu.
Perhaps the whole card might draw close to 100W, but i doubt just the GPU specifically.
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These 70W figures that various reviewers are coming up with are measured at the wall, as in card installed vs card not installed.
Mind you, the PC's PSU which powers the card is itself only ~80% efficient, so our 70W at the wall is more like 56W coming out of the PSU into the PC.
Then the video card itself has to step down the voltages, as it's being fed 5v and 12v, and the GPU core and memory don't run at these voltages. Around another 10% gets lost here in the voltage step-down, so our 56W being fed to the card is more like 50W actually consumed by the componentry on the card.
Then we get to the peripheral devices on the card, as in everything that is not the GPU and the memory, and we're let's say they all consume 5W together, leaving 45W of power being drawn by the GPU and memory.
A single piece of high speed DDR will be consuming around 1W of power when under load. There's typically 8 memory chips on a high end card, so that leaves us with around 30-35W of power being drawn by the GPU itself.
Now looking at the heatsinks which get fitted to 80-100W CPU's, and the heatsinks which get fitted to video cards, and given how hot the GPU's actually get under load (my finger is still aching from the last time I touched the back of my new stock air-cooled video card behind the core), we can guess that the 30-35W figure should be fairly close to the mark. I'd be leaning more towards 30W myself.
Now I'm not saying that the above figures are all accurate and occur in reality, but what I'm trying to highlight is that there's a pretty damn big difference between how much power is being drawn from the mains wall socket which is where these reviews are taking their measurements, as opposed to how much power/heat a GPU is actually using/generating.