The 380X specs that have solidly become consensus suggest an HBM-equipped, 4096 stream processor card that will far and away beat the 980X (
for example), and multiple alleged benchmarks all consistently fall in line with said specs with slight upward notching of more and more recent reports that's probability indicative of driver maturation. It will not, however, be power efficient.
We're not quite talking GTX 480 real world results back when TDP was more like a suggestion for Nvidia, but it's going to be close to those days. It's going to be around 300W, most people think it'll have some sort of closed-loop liquid cooling setup. In short, it will demand some serious PSU.
If the performance numbers are reasonably representative and the 295W TDP is correct, then we're talking a card with a ~40% performance advantage, but a ~80% power hike, or put another way, it uses roughly 30% more power per unit of performance. That's not night and day, but provided all those numbers aren't completely wrong, it's a difference, to be sure.
There will also be other tradeoffs between them. AMD will probably keep the hillariously better GPGPU capability that separates their cards from Nvidia's non-GK110 cards, but that's a niche concern for the moment.
In a way, this creates a good situation. It makes the cards from Nvidia and AMD slightly different products that have slightly different emphasis. I was going to get a 970, but now I'll probably get a 380X myself.
Edited by Catamount, 08 February 2015 - 08:23 AM.