........Once the Sun sets, I'll try getting the GPU to work again on Linux, for my AMD setup, see if that makes a difference, then go back to Windows and toss in another 2 1080s to see if that has any negative effect on that system, strains the BUS, etc.
Uhm....forget about going back to Windows. The first few tasks under Linux Mint Cinammon 18.2, Nvidia driver 378 (oldest from the list), and the ppd was higher than similar tasks I'd seen run on the same system with Windows, avg of 80k ppd higher. Impressive, right?
Well, finally I have caught a 9415 task being processed, and have been watching for more than an hour now. As a refresher, the 9415 task is the one I personally have the most (mental) data collected for, and under Windows on this system, I lost 10k ppd, moving the 1080 from my E5-2695v3 system, and was seeing 650k ppd.
another edit in a few minutes....
......and I watched that task to the very end, and another 9415 started right behind it which I will have to keep an eye on, but, are you ready for this? 826k ppd on Linux, up from 650k on Windows, and the 2nd task is also estimating the same ppd!!!! The lowest estimate I saw while the first task was running was 809k.
....another edit, half way through the 2nd 9415 task and the ppd estimate is 'only' 806k, but still far in excess of a 20% improvement over Windows. I have to get out of the house now, so last edit.