iMac Late 2009 - Slow SSD, High Sierra Freeze, Bluetooth Crashes...

I've seen posts on these forums which mention compatibility issues with some older Samsung EVO SSDs especially with older Macs, but this can be a problem with a lot of other SSDs as well. Most SSDs are SATA III, but some of them have trouble auto-negotiating the slower SATA II link speed so it can cause problems. The only SATA II SSD that I'm aware of these days is the OWC Mercury 3G SSDs. I have used the Crucial MX series SSDs on some older Macs without issues, but not enough to be completely sure of their compatibility. If I'm in doubt and cannot risk compatibility issues, then I will chose the OWC 3G SSD to be safe.

If you want to check the health of the Samsung SSD run DriveDx and post the report here using the "Additional Text" icon which looks like a piece of paper.

I recommend running Disk Utility First Aid on the hidden Container. Within Disk Utility click "View" and select "Show All Devices" so that the hidden Container appears on the left pane of Disk Utility. Even if First Aid shows everything is "Ok" click "Show Details" and manually review the report to look for any unfixed errors. If there are any unfixed errors you will need to erase the whole physical drive before restoring from a backup or clone.

If the SSD looks healthy and First Aid is clean, then you may want to try reinstalling macOS over top of itself (should not affect your data or your apps or settings).

The SSD looks healthy from the report and the firmware looks like it is at the latest version as well. Try booting into Safe Mode and running the SSD's selftest again with DriveDx to see if it will finish. The fact that the short selftest is aborted indicates the system is accessing the drive too much so that the selftest is unable to complete (the test only takes two minutes to run usually). If the selftest completes while booted into Safe Mode, then you have some software issue causing your problems since Safe Mode disables third party drivers, Startup Items, and Login items as well as even some Apple drivers like a built-in camera.

As far as the missing HD temp sensor this could theoretically cause the Mac to run slower since Apple does run the fan at high speed to help protect the Mac from overheating due to not being able to monitor system temperatures properly. It is conceivable that the Mac could reduce the CPU frequency (aka speed) to help keep the Mac running cool, but I've never tested or measured it since I always replaced the bad or missing sensors.

If the performance issues are something new and Safe Mode works properly, then you most likely have a software issue of some sort even though nothing stands out in the EtreCheck report, although I am wondering about your memory configuration. What brand of memory are you using and is it listed as "Mac Compatible"? Plus what physical slots are the 8GB stick installed? IIRC they should be installed side by side (left and right slots of the same row). Macs are very picky about the memory they use so it is best to only use memory from Crucial or OWC (and then only the exact parts listed by the tools on their respective websites).

I don't see any of the usual suspects in the report.

I'm afraid your iMac is just slowing down due to age like yours truly.

Performance:

  System Load: 1.40 (1 min ago) 2.02 (5 min ago) 1.03 (15 min ago)

  Nominal I/O speed: 0.00 MB/s

  File system: 21.20 seconds

  Write speed: 261 MB/s

  Read speed: 272 MB/s

Those Read and Write speeds should be much higher for an SSD. Did you replace the HD inside with the Samsung SSD or is it an external SSD? Did you do the work yourself as it would't be cost effective to have an Authorized Apple Service Provider do it.

When did you first notice the slowdown in performance? Was it after any system updates or software installs or updates?

Personally I would seriously consider getting a new replacement for that model which is considered obsolete by Apple. That means Apple won't work on it. You'd have to go to an Authorized Apple Service Provider and they probably would have trouble getting replacement parts.

The report indicated a number of apps crashing. boot into the Recovery volume (boot with the Command + R keys held down), select Disk Utility and repair the drive. If you get any error reports rerun Disk Utility until there are none. Reboot normally, run for a bit and see if there's any improvement.

If the HD is a 5400 rpm model it wouldn't help to replace it as it would run even slower than the SSD is running now.

If budgetary concern limit you there are some Apple refurbished iMacs that would be definitely a step up from what you have:

iMac 1

iMac 2

iMac 3 - 27"

The 27" iMac can have the RAM easily upgraded by the user.

The SSD looks good. I would not reinstall macOS until we confirm the memory situation.

I'm not sure how to read or interpret the layout shown in your picture since I don't know how it relates to the physical layout. If the picture actually represents the physical layout, then the memory is installed incorrectly which can lead to a huge performance hit. When you installed the memory upgrade was the memory installed side by side (left & right) which I think is the proper layout or did you install the two 8GB modules front & back? If you are not sure, then remove two of the modules to see their physical layout. If the memory is installed in the wrong physical layout you can get a huge performance hit.

Also what is the make & model of the memory upgrade?

Old Toad wrote:

I'm afraid your iMac is just slowing down due to age like yours truly.

Performance:

  Write speed: 261 MB/s

  Read speed: 272 MB/s

Those Read and Write speeds should be much higher for an SSD. Did you replace the HD inside with the Samsung SSD

The SSD speed is actually very good since this iMac (late 2009) only has a SATA II controller which is 3Gb/s so it has a max speed of 300MB/s.