iMac 27 2011 ssd constantly freezes, hdd works fine

vjson

macrumors newbie
Original poster
Feb 13, 2020
4
0
Hi everyone,

I purchased a Samsung 850 evo 500GB ssd and followed the OWC ssd upgrade instructions (using the supplied cable in their upgrade kit) to install it as a second drive. The original hdd and the optical drive are also still in the system and both work as they should.

When accessing the ssd (either running high sierra on it or even just using it as a storage drive while running high sierra from the hdd), the system constantly freezes for up to several minutes, but sometimes only around 20 seconds. The cursor still moves, and switching windows usually also works, but the app that is accessing the ssd remains completely unresponsive and seems to do absolutely nothing until it suddenly continues as if nothing had happened.

No kernel panics, no crashed apps, no heavy cpu processes or memory usage, just very frequent freezes that clearly only happen when the ssd is being accessed.

I have erased and re-installed high sierra (and even Catalina using dosdude patcher) countless times, but nothing helps. Running the system on the old hdd works perfectly and hasn't frozen even once in years.

I have searched all over the internet including these forums, and while there are quite a few people who seem to experience the same problem on their ssd, I have yet to find any solution. The only thing I haven't tried is replacing the ssd or the OWC cable since I don't have any replacements, but it doesn't seem likely to me that those brand new products would be faulty.

Does anyone have any clue what could be causing this annoying behavior that's making my ssd completely unusable? I greatly appreciate any and all suggestions and ideas, thank you!

UPDATE:
The iMac freezes regardless if the SSD is connected internally via SATA or externally inside a USB2 case, which rules out a faulty SATA cable. HOWEVER, when connecting the USB enclosure to my MacBook Pro 2015 and booting from it, the system seems to be working fine without any freezes so far.

So, iMac only and always works with the standard HDD, and always freezes with the SSD (both via SATA and via USB), but the SSD seems to work fine when connected to my laptop via USB. I am stumped. What could possibly be the problem then?
 
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vjson

macrumors newbie
Original poster
Feb 13, 2020
4
0
You have not given any details about youre Imac but with USB2 it is too slow for an SSDS sauch as the850. And the patcher may also be the problem.
iMac 27" Mid 2011
3.4GHz i7 2600
16GB RAM (4x4GB)
AMD 6770M 512MB
2TB HDD
Samsung 850 EVO 512GB SSD

iMac, SSD (internal) => freezes
iMac, SSD (via usb) => freezes
iMac, HDD => does not freeze
Macbook Pro, SSD (via usb) => does not freeze (this is what stumps me, as the iMac behavior suggests a problem with the SSD itself, but that seems unlikely because it works fine on my macbook)

The system freezes constantly both during typical usage (navigating in the finder, opening a menu, etc) or heavy disk access (copying files, launching apps, etc). The low speed of USB has no significance, as it is still way faster than the internal HDD, and still freezes on the iMac but does not freeze on my laptop.

The freezes occur both on High Sierra (standard install) and on Catalina (using dosdude patcher).
It also seems to be unrelated to the OS because even when formatted and only used as an empty storage drive without any OS, it freezes randomly when being accessed, e.g. reading or writing files to it.
 
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