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iMac (27-inch, Mid 2011) restarting unexpectedly

Hi, was hoping to get some assistance in diagnosing an issue I am experiencing with my iMac. It seems that after an hour or so of use I experience the screen flickering with vertical lines and intermittent restarts with no error. I recently booted up this machine after it was sitting in storage for a couple months. Seemed to work fine prior to this. As soon as I booted it up I performed a factory reset and since then this issue has been occurring. Any assistance is greatly appreciated.



Posted on Apr 13, 2023 6:09 PM

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Question marked as Top-ranking reply

Posted on Apr 13, 2023 7:30 PM

Crashes seem to point to Memory.


Have you blown the dust out of the intakes lately?

What temperatures does this App report? Especially the GPU & CPU.

This App can be used to speed up the fans, all my iMacs would be dead without it.

Never ever ever drop fan speeds below the speed that the Mac itself is calling for.

MacFansControl…

https://www.crystalidea.com/macs-fan-control


You can use Drive DX to possibly get a better view of Drive health…

https://binaryfruit.com/drivedx


Thanks to Jack-19…

It may be wise to run SMART Utility to check the drives' health. 

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11 replies
Question marked as Top-ranking reply

Apr 13, 2023 7:30 PM in response to asieffert

Crashes seem to point to Memory.


Have you blown the dust out of the intakes lately?

What temperatures does this App report? Especially the GPU & CPU.

This App can be used to speed up the fans, all my iMacs would be dead without it.

Never ever ever drop fan speeds below the speed that the Mac itself is calling for.

MacFansControl…

https://www.crystalidea.com/macs-fan-control


You can use Drive DX to possibly get a better view of Drive health…

https://binaryfruit.com/drivedx


Thanks to Jack-19…

It may be wise to run SMART Utility to check the drives' health. 

Apr 14, 2023 9:47 AM in response to asieffert

I agree with BDAqua that RAM seems to be an issue, and that RAM has been added. What is the make of the added RAM?


Most senior contributors here only use RAM from Crucual or OWC in Intel Macs. The cheaper "Value RAM" that is so prevalent from other vendors does not always play well with Macs, even though advertised as being Mac-compatible.


🔶 An incidental finding not related to your current issue:


Drives:

disk0 - Samsung SSD 860 EVO 1TB 1.00 TB (Solid State - TRIM: No)

Internal SATA 6 Gigabit Serial ATA


Your after-market SSD option is wise, and is running right on the nominals:


Performance:

System Load: 1.88 (1 min ago) 2.39 (5 min ago) 1.46 (15 min ago)

Nominal I/O usage: 0.60 MB/s

File system: 17.64 seconds

Write speed: 508 MB/s 👍🏼

Read speed: 529 MB/s 👍🏼


However, TRIMForce is not enabled. What we are seeing is that, at some point, Write speeds in these aftermarket SATA drives starts to decay. It is independent of drive make.


For the OWC Electra SATA 6 SSD in my 2012 Macbook Pro 13", the slow-down took about three years to appear. When it did, the Writes first went to ~250MB/sec (1/2 the Read speed) and continued to drop as low as 60MB/sec, just as slow as the old pokey hard drive the SSD replaced.


With the help of our amazing Grant Bennet-Alder, enabled TRIMForce and then had to do quite a Safe Boots before the Writes returned to normal, but they have stayed on the nominals since.


Information I used to enable TrimForce is here:


https://eshop.macsales.com/blog/31619-how-to-execute-trimforce-command-with-your-owc-ssd/



iMac (27-inch, Mid 2011) restarting unexpectedly

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