Here's my quick update on AVX and iMacPro1,1:
No performance changes on iMacPro1,1, unlike Pete. I used basically the same config.plist as for 18,3, but I had to explicitly enable the Nvidia WebDrivers, otherwise they would not be used. Interestingly, I was able to install and to run the system without the Nvidia drivers with the 1070. But in therms of hardware compatibility, there were no real improvements. I have a couple of USB 3.0 ports that are not recognized with iMac18,3 (couldn't be bothered to implement a patch), and they are still not recognized now. Everything else seems to work as expected. Sleep and wake and restart all seem to work fine.
About AVX: What a change! I spent a couple of hours doing stability tests, with Cinebench, Geekbench and Prime95, and here's what I found:
OC @ 4.4GHz
Core Voltage @ 1.12V (down from 1.21V!)
AVX 512: -2
Cinebench maintains the score at around 1920 (I even had a run with 1930, but I was not able to reproduce). However, the temps go down by 9C, to around 91C. Great improvement!
Because the score doesn't change, I suspect it does not use AVX.
Geekbench goes a bit lower: 5499/35888. I used to have 55xx/36xxx. So not much of a difference, but this makes me assume that some of the tests use AVX.
Prime95 is stable, at least for the 20 min I let it run the Torture Test (one pass of all 4 tests). Temps are also lower by about 5C, but it does use AVX all the time, so performance is at 4.2GHz. There was one test that still had a bit of throttling.
So all in all, very good results, what an improvement in the temps! Besides the suggestion from surfinchina to lower the AVX, I suspect the new BIOS version also helps on stability.
I still want to test further. I haven't found the lower voltage that maintains stability yet, I didn't have time. I know I can't leave it on auto with 4.4GHz, that I tried and didn't work.
I also tested how low I can go:
* Auto voltage at 44x is too unstable. The system reboots as soon as I try Cinebench.
* 1.11V is a bit stable. The system rebooted only after 5 min of Prime95. It worked through Cinebench and Geekbench without any apparent issue.
Also, tests on Windows were very similar, except for Prime95. There the temps were too high, and the processor was throttling down to 3.7GHz half of the time.
Once I have a more definite answer on voltages for this minimal OC, and when I move to iMacPro1,1, I'll update the main two post to reflect that.
Thanks for all the help!
On another news, I just noticed that KGP started his massive guide here too: http://www.insanelym...extended-guide/
I wonder how it will work out. I hope it doesn't burst into flames so quickly this time ;-)