I recently switched from an old iMac 2012 to the new Mac mini 2018 (i5 6 core). I was very surprised (and annoyed) to find out that some of the FF plugins work much worse on the new system than on my old system. I have 10 instances of FF-R on a test project. Ableton shows about 50% CPU and cannot play w/o crackles. On my old system this was no problem.
It seems to affect FF-R and FF-L, but not FF-Q.
Somehow it seems to interfere with the graphics. The problem almost disappears when I minimize Ableton. Also the CPU usage goes down then (MacOS activity monitor). All plugin windows are closed during this test, btw.
I already tried to disable the graphic acceleration for FF plugins. But this did not help.
I know that the Mac mini has a crappy GPU (Intel 630). But I would not expect to see any interferences with audio plugins and their CPU usage.
I repeated this test with another VST/AU host (NI Maschine). Same problem.
This is really puzzling. If the plugin interface is closed, the interface doesn't exist and therefore can't use any graphics resources. This pretty much rules out any GPU problems. (The graphics usage should never interfere with the audio thread anyway.)
Depending on the preset, it's quite possible for ten instances of Pro-R to max out the system. Do you use the same buffer size and other audio settings? Same audio interface? Do you put the ten instances one on track, or on different tracks?
For the test project I just used the default preset. The instances are on a different track each. Most tracks do not produce audio. I have only 3 tracks w/ actual audio. Other tracks are silent.
And yes, same buffer size and interface.
Regarding the graphics: A support guy from Ableton asked me to test if different screen resolutions and/or minimized window makes a difference. That's why I did this test.
I'm not an expert about the Intel UHD 630 GPU. I know that this is kind of embedded into the main CPU chip and also shares RAM with the main system. So chances are that some other resources are also shared. So that increased GPU usage (from DAW main window) also affects CPU in some way. But that's pure speculation from my side. :)
I'm considering to test if a eGPU would help.
even though it sounds strange: I can confirm that using an eGPU (Sonnet Puck w/ RX 570 in my case) completely removed the performance problems on Mac mini 2018.
Thanks for the feedback! That is quite odd... almost looks like the integrated GPU really holds the CPU back (maybe via shared memory?) if they're both working relatively hard.