iMac 5K Retina extremely slow Mission Control

If you can do without the animations in Mission Control, the following will fix the lag issue without disabling transparency, increasing contrast, changing resolutions, etc. You don't get the eye candy but it's really fast without changing the look and feel of the desktop - no lag.

Enter in Terminal app without quotes: "defaults write com.apple.dock expose-animation-duration -int 0; killall Dock"

If you're not comfortable with the Terminal app, it can also be changed with TinkerTool (in the Application tab, under Mission Control, Speed of animations) - set to "Disable Animations".

ok i disabled the animations, but i don't like the sudden transitions, a bit jarring. so i re-enabled 'Default' animations, and also enabled 'Increase Contrast' in the Accessibility panel. this helps reduce the lags, but Mission Control is still not behaving nicely. i hope this bug is on Apple's to-fix list.

To set Mission Control animations back to defaults, enter the following:

Enter in Terminal app without quotes: "defaults delete com.apple.dock expose-animation-duration; killall Dock"

I've updated to 10.10.3 and there is still a distinct lag between normal and Increased Contrast! With Increase Contrast the transition is perfectly fluid, without it, it is laggy. I can't believe this still isn't fixed.

I'm sorry, but I can't help but laugh at all of these alleged "FIXES" for this problem. Sure, it's always "FIXED" after you reboot your machine. Can anyone honestly say that they've had their 5K iMac running with 5 or more programs for more than 8 hours, and Mission Control has no lag? I highly doubt it. I also highly doubt that Apple is working on this problem. There just are not enough complaints about it. It sure seems like it's a 5K resolution / Yosemite problem. I've already given into the fact that this is something that I've gotta deal with, and have ZERO hope of this thing getting fixed before I move on to my next iMac in a few years. 😐

I can honestly say that it is a lot better, although not nearly 100% fixed.

I have been running my iMac 5k for over 4 days now: 11:55 up 4 days, 17:03, 2 users, load averages: 1.42 1.83 1.84

Right now, I have 15 applications open, not counting anything on the menubar, and while the lag is still there, it's better with 10.10.3 than it was with .2 or .1.

I still have TotalSpaces installed and find myself using that from time to time; it's not the same, but at least there's no lag - which again proves to me that it's software, not hardware.

I agree that it could and should be much better, and hope that 10.10.4 or .5 or whatever does address it, but I also think that despite how it impacts us, we're a small sample of the total population, and just aren't making enough or the right kind of noise.

- Scott -

the Increase Contrast / Reduce Transparency workaround DOES HELP minimize the GUI lags with Mission Control. it's not perfect, you might get an occasional 'hiccup', but MC behaves noticeably better when these two Accessibility options are enabled.

the MC bug has nothing to do with 5K machines, as it also effects my late-2009 27" iMac, along with many other models. from what i've deduced, this is a widespread problem, and only with Yosemite. Mission Control in Mavericks (and previous MacOS versions) worked flawlessly. no lags whatsoever. this is strictly a Yosemite bug, not your iMac.

i can't understand why Apple hasn't fixed this yet. i've certainly complained enough about it, and submitted a bug report describing the problem.

For what it's worth, I've also submitted a new bug report today for this issue. If we keep reporting it, maybe they'll finally fix it to shut us up 😉

i also use TotalSpaces, and it behaves exactly the same way as Mission Control does when Increase Contrast is not enabled. i was hoping that TS would solve the problem, which is why i bought it, but nope. can you confirm that TS on your machine doesn't lag when Increase Contrast & Reduce Transparency are not enabled? try it again, i'm curious.

Man am I glad that the reduce transparency / increase contrast option at least HELPS. Just for the heck of it, I just unchecked those boxes. WHOAH!! My 5K iMac practically locks up. It took nearly 10 seconds for Mission Control to kick in. This is SO **** unacceptable for a $3500 computer! Like I said though, I just don't see a fix for this thing anytime soon. Maybe after Yosemite? Ugh! 😐

I have Reduce Transparency enabled, but not Increase Contrast, and have no lag at all w/TotalSpaces.

HOWEVER - and this is a big however - as soon as I turn off Reduce Transparency and try TotalSpaces or Mission Control, everything goes to **** - so much so that I have to restart my Mac as it just doesn't recover at all.

Thanks,

- Scott -

on my iMac, Increase Contrast must be enabled (Reduce Transparency gets enabled by default when Increase Contrast is selected), otherwise both Mission Control and TotalSpaces behave like *****. i checked again a few minutes ago, just to be sure. i'm using the latest version of TotalSpaces.

My iMac has been running lag free for over a week with Mission Control animations disabled - the "instant" window display may not be for everyone, but it's fast - every time. As always, mileage may vary.

After using the new OS X for a few days, the problem is still there. Even with Reduce transparency and Increase Contrast on. I have the fastest processor, the faster graphics processor and 32GB RAM. So basically the max config for this iMax and it's still slow as ****.

I just tried a view things on the 5k-imac in the apple-store: open 5 or 6 fullscreen windows with safari and the apple imac-page open. Already with that MC is very laggy.

Dear apple, I really want to buy a 5k, but only if I can get a working hard+software for my money! I hope this will soon be possible...