I had been using VMware Fusion 7 on my iMac running OS X Mavericks with no issues. However after upgrading to OS X Yosemite my VMs had severe performance problems to the point where the characters I typed in a terminal wouldn’t show up until I waggled the mouse.
A little bit of Google-Fu led me to this thread on VMware’s community forum, however I wasn’t prepared to make the suggested changes to my NVRAM without understanding a little more. Reading through the thread I was led to similar thread on the Parallels forums suggesting the same fix, but with no more explanation. The thread did contain a link to a Parallels Knowledge Base article that explained suggested the exact issue I’d seen could be due to interrupt storms. Even better they linked to another knowledge base article that explained how to confirm this theory.
Having followed the steps on my iMac I confirmed that I was seeing interrupt storms relating to the
com.apple.driver.AppleACPIPlatform driver. This finally led me to a thread on Apple’s support forum that suggested the same fix.
After applying the fix the performance of my system was like night and day! I hadn’t appreciated quite how badly it had been running even out with VMware Fusion.
If you’ve made it this far you probably want to know what the fix is? Open a terminal and type the following:
sudo nvram boot-args="debug=0xd4e"
Once you’ve done this restart your iMac and it should be significantly faster! If this works for you please raise a support issue with Apple so that they address this properly in a future update to OS X Yosemite.
The only troubling thing is that I still don’t know what setting “debug” to “0xd4e” actually does…