Massive freezing problems with Mavericks

I'm in for what's now my 5th repair on my early '13 15" 2.7ghz/512gb/16gb system.... They're replacing the logic board again due to the freezing, I guess my logs showed a lot of GPU crashing... Sucks so much, I've lost so much time taking it in (would estimate they've had my computer no less than a month) and just all the time I've spent testing and reading forums to no avail..... This machine ran fine on ML, just the UI lag was abysmal compared to Mavericks due to the retina display.... This $3k laptop has been above and beyond the worst I've ever owned, we still have a late '11 15" (the one that is supposed to have GPU failures) and it runs like a champ as well as a '12 mac mini, '11 13" mba yadda yadda.... Something about this specific hardware locks up with Mavericks, and I'm not sure what it could be....... They've replaced so much, maybe it has something to do with the power brick or the battery, I have no idea..... It's so intermittent too, can happen once a day, or even have had 2 weeks of uptime before it's happened. Blargh.

I've noticed the same thing at my work. We have hundreds of 2012 model MacBook Pros, as well as earlier silver iMacs. I find that on every single one of them when running Mavericks, there is an incredible amount of lag on first login after booting up, especially if it's a new user. To the point where I log in, the desktop and finder load, I click on the Apple logo to logout or shutdown and it takes 30-60 seconds for it to unfreeze and display the menu.

It seems to happen with any computer running a mechanical drive. Once I upgraded my personal MBP to an SSD, the thing flies.

Early 2008 iMac Freezing

Well, they did it again. The latest Mavericks' update (Sept 24, 2014) that's supposed to "Improve Stability" (?) is crashing (freezing) my iMac.
Why, you ask? Because the update, once again replaced the WORKING Ati .kext files with AMD .kext files that cause the computer to freeze!
Didn't take long this time. Almost got through the "Optimizing" notification when it locked up.
Replaced the AMD drivers with the older ATI drivers that came with the computer and voilà, no more freezing!
Huh, imagine that!
You have to be fast. Fortunately, the update doesn't remove the older ATI graphics drivers. It just loads the new ones and doesn't load the old drivers. I just went into the system extensions folder and trashed the AMD .kext files and rebooted.
Problem once again solved.

same effect

Because the update, once again replaced the WORKING Ati .kext files with AMD .kext files that cause the computer to freeze!

Click to expand...

Yes I can confirm all, every updates replace the kext files and every time we need to re-load the olds.

I want to ask if this "workaround" still working on Yosemite.

I'm wondering to update, because my iMac 8,1 with 6GB RAM and SSD run lovely with Mavericks 10.9.5.

Maybe someone else can answer this. I haven't upgraded to Yosemite yet. I tend to wait a few months to see if there are any bugs similar to the IOS 8.1 failure.
I wouldn't be surprised though if the same updated AMD .kext files come with Yosemite. Seems to be a security hole in the old drivers when surfing to a compromised site.
You just have to be careful where you go.
Also I noticed that if for some reason your Mac takes longer and longer to boot up, unplug your back up hard drive.
My SSD would only take about 15 seconds from start to desktop. If I forgot to unplug the backup drive, (even if turned off) it would take longer and longer to boot.
I only plug it back in when I need to do a backup.

I can conform that in Yosemite too we have to replace kext for iMac 8,1 with ATI 2600.

After that the system is very very fast, flowing and stable.

At the moment we have not encountered any problem.

See you