Use of a Windows Diagnostic Tool on my iMac HD by a Technician

1) EtreCheckPro is an excellent tool for finding software and hardware problems.

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post your Report, as per > How to use the Add Text Feature When Post… - Apple Community

2) If it is crashing and restarting when you wake it from computer sleep mode.

Then test the following Energy and Lock Screen Settings.

Turn On "Prevent automatic sleeping when display is off"

Set "Turn display off when inactive" to 5 or 10 minutes

Leave the iMac On and only allow the display(s) to turn Off

Do not manually Sleep from the Apple Drop Down menu

Shut Down the iMac when your away for a day or more

lifewebb wrote:

Re. Etrecheck - I am amused to inform you that I did try that and it immediately crashed! Twice. Would not do its work. Nothing I could do! I think I have a report for that one.

Startup in Safe Mode, as per > Start up your Mac in safe mode - Apple Support

Then see if you can run EtreCheckPro.

den.thed wrote:

1) Where did you get those 16GB RAM modules.? They look OK.

Although you might want to swap the modules in Bank 1 and Bank 2,

so that the 16GB modules are on DIMM 0 and the 4GB modules are on DIMM 1.

https://discussions.apple.com/content/attachment/c5343b01-a307-4242-a9b9-dba96fd843e3

I was thinking the same thing, but I recall several years ago where installing the memory in the configuration the OP has actually gained extra performance....plus a high level forum contributor had mentioned it was the correct configuration when I pointed out pairs should be in DIMM0 slots, then in DIMM1 slots. However, you are correct that matched memory module pairs should usually be installed first in the DIMM0 slots and with extra memory into the DIMM1 slots.

Unfortunately I am not aware of any official documentation. Here is the Apple support article for installing memory into an iMac. The relevant section is Step #9 (the first Step #9 where the memory is accessed by the back panel) where it mentions you are correct in how the memory slots should be populated (the documentation is a bit confusing as is usual for Apple these days):

Install memory in an iMac - Apple Support

iMac (Retina 5K, 27-inch, 2020) DIMMs have a notch on the bottom, slightly left of the middle. If your DIMMs are mixed in capacity, minimize the capacity difference between Channel A (slots 1 and 2) and Channel B (slots 3 and 4) when possible.

I would also wonder about the third party memory upgrade since Macs are very picky about the memory they use. There is more to memory compatibility than the main memory speed since there are lots of other critical timings that Apple does not document so there is usually no way to confirm compatibility unless the memory vendor guarantees compatibility for the exact parts purchased. Crucial & OWC do this when using the tools on their respective websites to identify compatible memory for a specific model computer.

To add onto what others have said...

"ST1000DM003" indicates that this HDD is an Apple re-branded Seagate drive. The Linux HW project's collated drive statistics indicate that the stats for this model are:

• Samples - 81;
• Avg days / sample - 800;
• Avg errors / sample - 55;
• Avg MTBF in years - 1.87

The project includes large scale data from Google, Backblaze and Acronis.

In other words, this HDD may be prone to failures - which the ridiculous power on count from Crystal Disks may indicate the reason for - a poor disk controller that powers the disk on and off too often.

Consider upgrading to a SSD. Your HDD is likely failing.

lifewebb wrote:

I could tell you that I bought two 16GB modules from Amazon MX, thinking that it would make the computer even faster and they were sold under a brand called TimeTec which allegedly were the correct ones for this iMac 2019,1 - 27 inch screen. Compatible with Apple DDR4 2666MHz / 2667MHz for Mid 2020 iMac (20.1 / 20.2) / Mid 2019 iMac (19.1) 27-inch with Retina 5.

I have seen mixed results for people using the TimeTec memory & SSDs.

Plus, memory very rarely increases system performance unless your workloads require it It is very easy to determine if memory is hurting system performance. Use the computer for days without rebooting while doing your tasks making sure to also perform the heaviest workloads.

Then use Activity Monitor to check the memory usage. If the Memory Pressure graph is:

• red, then you need more memory.
• yellow, then you are borderline on having sufficient memory
• green, then check the Swap Used and Compressed Memory...if they are in the GB range, then you probably need more memory (especially if it is more than 2GBs).

The file system issues can easily cause performance issues, plus the Fusion Drive is a bit of a limiting factor. Of course 8GB of original memory is very limiting except for the most basic tasks. I don't know why Apple sells sub-par configurations without a clear warning that such a system is for only very basic usage since most average users won't realize it.

I discovered that the 16GB modules had been made by the same manufacturer that Apple had used for its 4GB modules - SKhynix.

While the memory chips may be the same, that is not the complete story. The supporting electronics on the memory stick must also be of high quality. Typically the minor players will skimp in order to save money so they can sell their products for less to make them more attractive. Plus those Skynix chips may not be 100% quality...they could be chips that did not pass all the rigorous tests other memory manufacturers require.

FYI, lots of manufacturers, even good ones may utilize partially bad chips by bypassing the bad sections in order not to lose money. So lets say a memory chip can support 4GB, but a 1GB portion is bad, they may use the remaining 3GB section. Usually that is not a problem if section used is 100% good.

It was a test of my own devising. Now the RAM consists of two 16GB blades which are correctly installed as the first two modules at the bottom of the tray. However, the day after doing this change, the computer again crashed and its report said 'Possible memory corruption'! So, I am no further on with whether the physical RAM is causing trouble.

The memory should be installed in the 2nd slot from the top and the bottom most slot IIRC. That should be the way the memory was installed from the factory. I've never seen memory in an iMac from the factory installed in slots next to each other.

Run MemTest86 to see if any issues are detected. Unfortunately the free version of the app is limited to just running the test in four loops each time, however, it can still have a good chance at detecting a memory related issue. With 32GB those four loops will likely take a day to complete (perhaps longer).

I would suggest reinstalling the original Apple memory back by themselves without the TimeTec modules to see if MemTest86 detects any problems and to see how the system performs. It is also possible the mix of Apple & TimeTec modules together is the problem....sometimes memory is not compatible with other memory. If you use both at the same time, then I would alternate the slots used by the Apple & TimeTec modules so matching pairs are in the DIMM0 slots and the other matching pair in the DIMM1 slots.

FYI, it can be very difficult to troubleshoot memory related issues unless the failure is extreme or very repeatable.

It would be pure guesswork of little use one way or the other. FWIW, I’ve used the utility on Windows and it does absolutely no harm other than to query the disk for already saved information and display it in usable format.

What you can do is to reset your Mac to factory and reinstall apps afresh and see if that restores normal operation. Be careful not to involve Time Machine during any part of resetting to factory: manually copy data files like docs and jpegs and PDFs to external disk for restoring later.

Before trying all that, see if you can get lucky with the settings below set exactly as shown (restart after changes).

Additionally, make sure your displays is set to sleep on timer in case you forget to lock your computer between breaks:

1) Where did you get those 16GB RAM modules.? They look OK.

Although you might want to swap the modules in Bank 1 and Bank 2,

so that the 16GB modules are on DIMM 0 and the 4GB modules are on DIMM 1.

2) Google Chrome is a huge resource hog and is causing issues.

Uninstall Google Chrome and use Safari or FireFox instead.

3) The Report does not indicate a problem with either drive in the Fusion Drive.

After you do those things, run it for a day or two, then run and post another EtreCheckPro report.

The only way, unless I'm missing something, would be if the tech connected the hard drive to a Windows system which if the iMac was disassembled was probably what was done. As you say, CrystalDiskInfo is a Windows-only utility. Without knowing what else the tech might have done with the drive, I can't say that it's impossible that he/she caused a problem with the drive, but I don't think CrystalDiskInfo itself would have done that.

There are a number of reasons beyond the hard drive that your mac might be experiencing constant crashes, but if you erased the drive and reinstalled macOS from scratch and it's crashing just with the base OS, then it's likely to be a hardware failure of some sort, such as bad RAM or a failing processor. But given the number of errors that the disk utility reported - note what to me seems a high rate of read errors and uncorrectable errors - a failing hard drive would be my first suspicion. That the utility reports "Good" as the health status may just be the S.M.A.R.T. status and not actually a verification that the drive is not malfunctioning.

Regards.

lifewebb wrote:

varjak paw wrote:

The only way, unless I'm missing something, would be if the tech connected the hard drive to a Windows system which if the iMac was disassembled was probably what was done. As you say, CrystalDiskInfo is a Windows-only utility. Without knowing what else the tech might have done with the drive, I can't say that it's impossible that he/she caused a problem with the drive, but I don't think CrystalDiskInfo itself would have done that.

Thanks, but how could a Windows software be applied to an Apple HD? Did he erase the whole thing - nothing Apple left on it and then format it to be used by Windows in order to use the Windows software? Then erase again and install OS Sonoma from one of his hard drives? Because it definitely did not come from Apple directly as it was not up to date. I have checked Sonoma version Release dates and other software like Image Capture. I got an old version of Image Capture which does not work properly! And the latest version of Sonoma was not installed, I had to download it myself.

I think that is what must have been done. Since there are Mac compatible softwares to do the same diagnostic, I am just astonished that the HD has been 'fiddled' with in this way and it has generated mistrust about a change being made to the HD and some kind of 'residue' of formatting being left behind, messing with the operating system and with apps. Chrome is not behaving normally now either, for instance.

He would have removed the drive and connected it to a Windows system via a SATA interface. That's the only way he could have run that utility. While I can't say for sure, he may well not have erased the drive at all, but if he did, he would have had to do it on a Mac. It can't be done from a Windows system. What exactly he did is impossible for any of us to say.

Again, I think a failing hard drive quite likely, as others in this thread have also indicated would be their suspicion.

Regards.