Hi all, I have a 2009 27" iMac (2.8Ghz i7 with 8GB) that over the last few months has become almost unusably slow. It's not what I would normally describe as slow though, it's kind of weird... some of the symptoms include: switching between tabs in Chrome will give me a white page for 10 or so seconds (as if it was using the swap file) even though I'd just been on that tab moments earlier the dock which I have on hiding will sometimes take a few seconds to display youtube/netflix videos will every so often freeze with the audio track still playing, then "catch up" really quickly (like I've hit the fast forward button) switching apps (eg. from Illustrator to Photoshop, or even to finder), will sometimes take several seconds, again even though they're actively used apps at the given time as part of my web dev work, I use gulp. On this machine it can take upwards of 10 seconds to run a compass task, whereas on my 2012 iMac at work (i5 with the same amount of RAM and old school HDD) will take less than a second for the same project file That's just some of the symptoms I can think of right now. At other times, the machine can be super fast as it always had been in the past, but it just keeps bogging down. I've investigated the common causes of slowdown that I can think of: HDD replaced in November 2014 because the former (stock Seagate) had SMART errors. Gave the machine a fresh install of Yosemite, so it's not like years of gunk has accumulated in the system Activity Monitor shows no out of the ordinary CPU and excessive memory usage, even while it's bogging down. Most processes sit around 1-2%, with only the normal peaks you'd expect. I don't get any hangs or crashes that would normally be caused by hardware faults, everything seems to be operating normally... just at a snails pace compared to what it used to be. Can anyone suggest anything that I should be investigating, or any tests I should run? I'm going to be upgrading to a new MBP in the latter half of the year, but I'd like to try and get this one back to it's former glory to get me through the next few months with ease. Many thanks in advance if anyone has any ideas!