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Question: iMac 2013 - SSD Upgrade - Poor Performance


I have upgraded the internal hard drive on my iMac with an SSD (Crucial MX500 - compatible drive).

I installed a clean version of High Sierra, drive formatted APFS.

First issue - the internal fan spun at maximum RPM. I installed Macs Fan Control to control it.

Second issue - the performance of the iMac is now very slow.

So, I installed a clean version of Sierra (drive formatted HFS+) and had identical issues.

I've enabled/disabled TRIM, tested the SSD with various software (all positive), reset SMC/NVRAM.

I've attached an Etre System report and frame grab of the Activity Monitor.

Is there something I'm not addressing?

Thanks in advance,


iMac 27 inch, late 2013

3.4GHz i5

16GB 1600 MHz DDR3

NVIDIA GeForce GTX 775M 2 GB

iMac, iOS 10.3.3

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Mar 15, 2018 9:42 AM in response to simoncrucialmx500 In response to simoncrucialmx500

Hello simoncrucialmx500,

The only known way of upgrading the internal hard drive in an iMac is with one of the OWC kits. At a minimum, you need the OWC inline thermal sensor (OWC In-line Digital Thermal Sensor for 27" iMacs 2012). That seems to be the root cause of your problems. Once you get that, the machine should perform normally and you can uninstall the fan hack software.

Mar 15, 2018 9:42 AM

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Question: iMac 2013 - SSD Upgrade - Poor Performance