THIS WORKED!!!!
sudo nvram boot-args="debug=0xd4e"
Can someone explain:
1 - What exactly does this command do, and why does it help?
2 - What command will UNDO this when/if Parallels provides a fix?
I am NOT suffering from the interrupt storm issue, NOR does moving my mouse around speed up my virtual machine.
But I DO, however, have a mid-2011 iMac 21.5" that is slugging with Yosemite in general, and worse with Parallels.
Thanks!
-- Matt Ryan