iMac 27" running really really slow - ran etrecheck in safe boot

Yeah; no obvious suspects.

Maybe a sketchy Fusion, if caused by hardware. I’d aim DriveDx at it, as a check.

For apps, I’d check for updates for XQuartz (may be benign and expected, but part of that is showing up as 2021, which is older than the most current version), and would also temporarily remove Dropbox, and disable or remove Adobe sync, restart, and test again. Sync apps can get all sorts of other things tangled.

I’m wondering whether the Intel processor is glitching. I’ve met a few bad Intel x86-64 processors on late-stage Intel Macs. Random apps just crash. And yes, as was mentioned by Allan Jones, third-party memory can also cause crashes. I’d try reverting to the Apple memory, if that’s a mix of Apple and third-party, as a test.

Do Apple Diagnostics show anything?

I'm not seeing a clear indicator of a suspect.

Unhappy standard or Fusion drives are the usual cause of slow iMac performance but these metrics:

Performance:

System Load: 1.49 (1 min ago) 1.06 (5 min ago) 0.50 (15 min ago)

Nominal I/O usage: 6.09 MB/s

File system: 19.64 seconds

Write speed: 692 MB/s

Read speed: 2585 MB/s

show me a normal drive. A healthy Fusion in your model should be doing Writes between 600 and 900MB/sec, and Reads should be 1300-2000MB/sec . Your Reads are above expectation. "File System" is a measure of drive system health and yours is quite comfortably within the "healthy" range.

You appear to have added RAM after purchase. What make was it?

Intel Macs are picky about RAM and can behave badly if the wrong RAM is used. With Crucial now apparently out of the Mac RAM business, the only place I will buy Mac RAM is from Other World Computing.

Known troublesome RAM we've encounter here are, among those with recognizable brands, the "value RAM' line form Kingston and Corsair, and PNY. To get compatible RAM from the first two, you usually have to order factory-direct, because most resellers only stock the lower-priced tiers that make for unhappy Macs.

You can try pulling your existing RAM in same-size pairs and testing.

When in doubt blame the Fusion Drive (Or Chrome). The SSD component is running properly but may be masking HDD issues. Or maybe you just have a -lot- of HDD stored data that is in active use trying to stay synced with the cloud. I've observed the HDD and cloud syncing doesn't always play nice.

What happens if you disconnect from the internet/cloud, wait a bit for stuff to settle, and retest offline?

Alternatively just assume it is the drive and buy a nice high capacity USB-C external SSD to use as your new startup drive for consistent fast storage. If it doesn't help you can always reuse the drive with your next Mac as either a Time Machine backup or just external storage.

low-life-clothing wrote:

Will give drivedx a try. Apple diagnostics comes back all clear. It has improved today after doing the update and starting up in safe mode. Not sure of the make of the ram it came like this when I purchased it a few years back

DriveDx might find something, as one of the symptoms of a failing HDD is beachballs, as the HDD gets slower.

But if it’s akin to the few bad Intel processors I've met in Macs, it just crashes anywhere and randomly, even with a clean install and no added apps.

Memory errors can (often do) cause crashes, but those usually have memory-related details with the panic crash reports.