Extremely slow SSD speed (iMac late 2015 27" 5K)

I want to use this iMac for music production (logic pro) but it's so slow it can't even do simple tasks like web browsing or messaging, it's useless. Disk (internal SSD) write speed is 13 MB/s, read speed is 40 MB/s. For some reason, if I let it run idle for like an hour it becomes somewhat useable. Here's what I've tried so far (none of these helped a bit):

did a clean install of macOS Monterey
took it to a repair shop (they were useless, they couldn't find a solution to my problem)
Enabled TRIM
Installed macOS on an external SSD (it was even slower than with the internal SSD)
Checked SSD health: no issues found, it's at 100%
Ran apple diagnostics: no problems found

Specs:

iMac late 2015 27" 5K
32GB RAM1867 MHz DDR3
4 GHz Quad-Core Intel Core i7
Graphics: AMD Radeon R9 M395 2 GB
2 TB SSD

Is there a fix for this? Thanks in advance!

iMac 27″, macOS 12.6

Posted on Aug 17, 2023 12:40 PM

Top-ranking reply

ku4hx

Level 7

23,802 points

Posted on Aug 17, 2023 2:50 PM

Per Mactracker, these are your drive choices:

There is no 2TB SSD, You have either a 7200 RPM HDD or 2TB fusion drive which has a very small SSD component and an associated HDD.

This means you slowness is likely a slow HDD. 13 MBps is dismally slow.

Download, instal and run etrecheck allowing full disk access and post the full report here using the "Additional Text" icon. This report will reveal all your mac's operational secrets of interest. It's a safe app.

https://etrecheck.com/en/index.html

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Extremely slow SSD speed (iMac late 2015 27" 5K)

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