iMac 5K Retina extremely slow Mission Control

Don´t know if it helps, since some users here have lags in mission control with 32GB ram, but the laggy graphics vanished completely on my base model 5k after upgrading from 8 to 24 GB. I have not noticed lags for several weeks now. I changed nothing else (software, drivers etc.) on my system.

Does the lag return if you remove the additional RAM? What RAM did you use?

I used Hynix 16GB Dual Channel Kit 2 x 8 GB 204 pin DDR3-1600 SO-DIMM (1600Mhz, PC3-12800S, CL11), the same brand as the original modules. I admit the suggested test would show, but I won´t fiddle with my modules, cause i´m not the DIYer type and happy with the results.

**UPDATE** I went ahead and checked the 'Reduce transparency' box under System Preferences>Accessibility and rebooted my new iMac 5K. It was a VERY noticeable improvement, and I was extremely pleased with the results of moving back & forth through my desktops, as the lag/stutter was completely gone. The animation with Mission Control was improved also, but it could have been better (like what I experience on my 3 year old iMac and 1 year old MacBook Pro Retina). But 24 hours later, the lag/stutter has returned, and it is painful to see. I really hope that Apple acknowledges this problem and will assure me that there will be a fix for it. Otherwise, this $3000 computer is going back to Apple. I'll just continue to use my THREE YEAR OLD 27" iMac. It's WAY better than this brand new 27" 5K iMac.

Status so far, for newcomers:

- 10.10.2 (as of 14C81h) doesn't fix the problem. It seems things improved a bit, maybe Apple is doing some experiments, but it's far being properly addressed.

- Apple is probably aware of the problem. Multiple posts confirm this, and I've exchanged some emails with a friend, senior programmer at Apple, who told me that it's likely they're working on the solution. But maybe they're not.

- Sometimes the system seems fine and responsive but it's an illusion. Over time it invariably degrades, immensely, to the point of forcing us a reboot, or insanity.

- Some people claim that apps running it the background make a diference, namely those that interact with the Finder or post icons in menu bar. I've found that reducing the number of app icons on the menu bar helps a lot. Keep them to a bare minimum. But the it doesn't fix the issue.

- RAM isn't the problem. I had the problem with 8GB and I have the problem with 32GB. Multiple posts confirm this as well.

- The GPU resources never seem stressed, I've been using some tools to look into it (iStat, OpenGL Driver Monitor from Xcode's Graphic Tools).

- Using a tool like SwitchResX and changing the screen resolution to 2560x1440 without HiDPI, that is turning retina off and using a scaled resolution, mostly fixes the problem, which is scary. And it's also horrible for your eyes, after you've been in HiDPI mode. But the system becomes usable, and work gets done.

- Reducing the exposé duration setting helps http://osxdaily.com/2012/02/14/speed-up-misson-control-animations-mac-os-x/ but it doesn't solve anything.

That's it.

4GHz i7, 32GB, M290X, dual monitor, 10.10.2 (14C81h) here.

Changing the setting to increase contrast fixes the issue 4 me, thank you for posting.

I have the base model $2499 and experience the same choppiness when using mission control. I have a late 2012 MB Pro 13" running 10.10.1 that runs smoother than the new iMac 5k retina. I'm taking this thing back to Apple and getting my money back. The fact is for a machine demanding this sort of price there shouldn't be issues with a function of the OS that is so basic. Not for me...

Also - if it were a software issue, why would my MB Pro running the same exact OS version as the iMac 5k not have the same issue. I agree with the previous post, it's a glitch...

I would say it behaves as if some operations in the WindowServer and possibly other OS services are not GPU accelerated. Maybe acceleration has not been enabled for not yet being stable enough - hoping for this being a software issue. Yet, this is pure conjecture.

Hello.

I don't know if this is anyway related to this Mission Control slowness, but does Safari on your riMac (16GB RAM, OS X 10.10.1 and M290X) corrupt pictures?

Reloadin page does not fix them but restarting Safari will. If Mission Control issue is a driver issue, perhaps this is also.

With 10.10.2 14C94b the drivers changed again, now its "AMD Radeon R9 M290X OpenGL Engine" again (no longer "Prototype", same as with 10.10.1) with the "Core Profile Version" "4.1 ATI-1.30.5".

I still have the issue with 14C94b (scroll a little up and down on http://www.apple.com/imac-with-retina/ and then open Mission Control and it lags).

I am afraid your post will be removed, as mine was because I referred to the latest beta version...

Was already wondering. We'll see, my last one about the drivers is still there.

With todays OSX Update the problem seems to be fixed.

I don't have any lags after 5 hours of work.

Yes, it looks better. I wouldn't go that far to say that it has completely solved everything, but it has become much better now.

I would say the iMac is now usable.

With the lags before I had the opinion it was not...