Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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Application startup very slow after boot

Apple iMac mit Retina 5K Late 2015


i just got the latest 27" iMac (late 2015) some months ago with smallest Fusion Drive. Right from the beginning i noticed very slow boot startup and application startup which made me feel a little bit disappointed. I guess it was the first start of the fusion drive and also file vault which i disabled immediatly.

Now the speed is okay when the machine is working for some time. But after boot alot of apps don't start for a minute.

E.g. Skype starts but doesnt connects at all. I have to force close, start again and wait 1 minute. If i wait 10 minutes after boot and then start Skype it works fine. Another example is WebStorm (programming IDE) which doesn't load at all for 1 minute. Same here: If i wait 10 minutes or so after boot it would start immediatly.

Chrome starts immediatly(loaded from SSD?) but doesn't load any website for 10-30 seconds.

iCloud Drive was not usable at all. Sometimes it just hung for 10 minutes when i want to copy a file out of it(copy wont start at all, no error message or something). I disabled it and canceled my subscription (Google Drive works fine).

I already formatted and made a clean install of macOS Sierra. Also i disabled VileFault and iCloud.

Also i noticed (may not refer to this question):

Most of the times when i shutdown the machine there is a bar of pixel-errors at the top of the screen from left to right while the rest of the screen is black. Also sometimes when i wake it up from sleep (hours of sleep) it just shows this pixel-error-bar at the top with rest of the screen black and doesnt load macOS for minutes! Sometimes it shows the macOS login screen after 5 minutes, sometimes the display turns off after 5-10 minutes and if i turn it on again it shows the login screen immediatly. Image:

Block Image

Maybe some of you have any idea whats wrong there. I know i can go to Apple Service Provider but 1. they may charge 70€ if they don't find anything and 2. its very unfavorable to transport such a big device without a car (public transport).

Answered! View the answer I have this problem too

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2 Answers

Chosen Solution

My first thought here is that FileVault is running in the background and either encrypting or decrypting. It has to either fully encrypt or, if it has been on and it is turned off, it then decrypts and I have seen this take over a day each way. If the computer goes to sleep it stops the process.

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Its disabled. Problem consists for months.


Btw Windows is running fine (HDD only)


You might find redoing the drive (reformatting) and restoring from your TimeMachine backup quicker.


Like i wrote i did this already but no TimeMachine just clean install


Sorry I missed that ;-{


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So i called the Apple Service. First off the pixel glitch is reported by many many users in the internet and seems to be a problem from Sierra. Nothing crucial at least.

With the Apple Service we deleted and recreated the Fusion Drive. The iMac seems to run very fast now:

First we startet Internet Recovery (If i remember right press CMD+R after starting the machine). Then we opened Terminal and deleted the whole Drive including recovery stuff.

  • diskutil cs list -> Copy Logical Volume Group UUID
  • diskutil cs delete <Logical Volume Group UUID>
  • diskutil list -> Copy Logical Volume Group UUID again and find SSD and HDD id's
  • diskutil cs create Macintosh\ hd disk0 disk1 (in my case disk0 = SSD, disk1 = HDD, found in previous step)

* diskutil cs createVolume <Logical Volume Group UUID> jhfs+ Macintosh\ hd 100%

Then close Terminal and start installing macOS. (In my case only El Capitan was available and i upgraded to Sierra later)

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