[These articles are labeled as rumors and AMD has not verified these findings. Take them with a grain of salt. This post will be updated when the rumors/leaks are confirmed true or false.]
20nm GPUs on the way: http://wccftech.com/amd-20nm-gpus-horizon-tsmc-ramps-20nm-production/
This is pretty freaking awesome (if it is true). 4096 Stream Processors (1280 more than the R9 290X), 4GB of High Bandwidth Memory (HBM), and the memory bandwidth is a staggering 640GB/s. That is TWICE as much bandwidth as the R9 290X. Freaking Wicked! Leak season is here y'all.
Am I the only one not impressed by the core clock speeds? 1.0ghz? When it's competitor is hitting 1.5ghz on air, 1.0ghz feels outdated to me. That speed says to me that they may still be having trouble as far TDP and power consumption are concern with their design. Plus, 4gb vram? 980ti is suppose to have 6gb on the get-go. I'm really being cautious with AMD at the moment.
Clock speed isn't everything as very Intel fanboy knows. So it is what they can do with it that counts. Plus, the new VRAM technology massively increases bandwidth which is really important in GPUs. Although, like you, I am a bit surprised that it will only have 4GBs. I heard a leak that suggested 6GB. So we'll see.
This is what's making me torn right now. I really could use a new GPU (7770 still does okay but is quickly loosing its ability to perform games on high/ somewhat ultra), but knowing that 16/14nm is on the horizon, might just wait out until the 400 series hits. But may still find a way to get my hands on a 390x to see how hard you can push it (Doubt you can too far, 20nm isn't the biggest improvement and with those specs they're probably pushing it already).
It is very unlikely for the 390X to be power hungry like past cards simply for two things: one smaller node (20nm) and two, HBM has very low power consumption.
it is HBM, not GDDR5. Massive difference in bandwidth and low power consumption. I am pretty sure they will make an 8GB HBM card in a few months after release.
offcourse you still need to be realistic, if you could use a new gpu right now, and you game on 1080p, then a card like a 390X will be totaly overkill.
So for 1080p or 1440p at the moment you should concider looking at the cheap 290´s. imo.
We don't know when these cards are coming out, might be soon though, looks like they are liquidating stock of their current been but that might just be price cuts to remain competitive.