Can Bootup speed be improved Monterey 12.6.7

I have recently upgraded my 2019 K5 27" iMac with a 2TB Adata SX8600 NVME SSD and a 2TB Samsung 870 Evo SATA SSD operating natively, (no Fusion).

I am satisfied the effort was worthwhile as operating speeds are close to PCIE 3.0 maximum, (Write 2,534MB/s Read 3,225MB/s).


However, the SATA drive Bootup time is 13 seconds while the NVME takes 47 seconds to load the same 200GB of system data. When starting to boot from the NVME, the Monterey progress bar runs to about 30% installation then stalls for about 15 seconds before racing to fully load the o/s. I am guessing that the alien NVME causes an startup disk initialisation conflict which explains the behaviour.


Is it possible that creating a Fusion combination would improve NVME bootup speeds - presumably at the expense of averaging out at lower operating speeds?


Alternatively, while I have zapped PRAM, is it possible to get a smoother/faster Bootup performance from the NVME with SMC tweaks via Terminal?


Any suggestions would be appreciated.


Posted on Jul 3, 2023 7:40 PM

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36 replies

Jul 9, 2023 9:29 PM in response to HWTech

Hi HW Tech,

The iMac now starts up into Samsung SATA SSD only. The NVME is registered as unmounted by Disk Utility and disk repair, erase and restore, cannot be used. For practical purposes the Adata NVME is dead.


I removed it from the iMac and replaced it with the 128GB Apple original NVME. The imac now functions fine with individual drives. (No Fusion). I am happy the iMac PCIE seems unaffected by the Adata NVME.


I have put the Adata into an external drive case, plugged in the iMac and tried again to restore it without success.

Do you think there is any method by which the Adata SSD can be reformatted or do we simply commit it solemnly to the Land of Failed SSD’s?




Jul 10, 2023 7:56 AM in response to Australopithicus01

Australopithicus01 wrote:

I have put the Adata into an external drive case,

What is the make & model of the external case? I have encountered a lot of enclosures over the years which are not reliable. Does this external enclosure support an NVMe M.2 SSDs? Just making sure you are not using an enclosure for an Apple OEM SSD where you are using an SSD adapter (another user recently did this while trying to troubleshoot which is why I am even asking).


plugged in the iMac and tried again to restore it without success.

How did you try to "restore" it. Do you mean install macOS to the external AData SSD or do you mean the "restore" feature of Disk Utility? The latter is not reliable, although Carbon Copy Cloner or SuperDuper are usually Ok (must follow their instructions....CCC requires manually selecting "Legacy" option). Installing macOS is the only reliable option especially when troubleshooting a possible hardware issue.

Do you think there is any method by which the Adata SSD can be reformatted or do we simply commit it solemnly to the Land of Failed SSD’s?

Make sure to erase the whole physical SSD. Within Disk Utility you may need to click "View" and select "Show All Devices" before the physical drives appear on the left pane of Disk Utility. Select the physical Adata SSD (it may be identified by the enclosure being used instead of as "Adata" when connected externally). Erase it as GUID partition and APFS (top option) if installing macOS 10.14+.


You can try to check the health of the Adata SSD by running DriveDx. You will need to install a special USB driver in order to access the health information of an external drive. Even with the special USB driver, there is no guarantee that the SSD enclosure will even allow the necessary communication to access the SSD's health information. Post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper.

Jul 11, 2023 6:43 PM in response to HWTech


  1. External case is cheap Chinese ‘No Brand’ which I used to format original ADATA. It does not support SMART.
  2. ‘Restore’ as in; run First Aid, run Erase&Format, and run Restore. All failed as disk would not mount. Since no mounting possible I did not consider re-installing o/s. My concern was to clean the drive.
  3. Drive showed in Disk utility under Controller model SM2262EN, not the original ID which was the name of the external drive ‘J Micron Tech Media’ being found by the firmware o/s at time of installation in iMac. As disk would not mount further action impossible.
  4. Drive X reports ‘Diagnostics of external drive unavailable’. External drive is too primitive. For that same reason Disk Drill cannot offer SMART monitoring.
  5. Seems I need to upgrade my external drive before and further diagnosis is possible. Do you have a recommended model to suggest-there is so much stuff out there and finding tech specs. not always easy.

Thanks again HW Tech

Jul 13, 2023 3:51 PM in response to HWTech

Hi HW Tech,

Thank you for the good information.

I have ordered a reduced price NVME case from UGreen with UASP and Trim. When that arrives I can consider results from Drive Dx and possibly test the Adata drive health.


Meanwhile, you may like to comment on the following:

Now I have replaced the Apple 128GB NVME and loaded Ventura operating system and Applications, (not enough room on SSD for my Account files), I find it takes over one minute to load 75GB!


Several hesitations and stops with the progress bar.

Black Magic tells me Apple NVME operates at write 740MB/s Read 2400MB/s. (Very poor Write time for a SSD).


So I still have this unexpected imbalance in SSD performance as I would have thought the Apple NVME SSD would have loaded faster than the SATA SSD. The Adata loaded in 47secs with 200GB of data because it was a much faster NVME but was still much slower than the SATA. I would not have expected this result. When iMac was previously configured with Apple SSD and the old HDD as a Fusion Drive, the iMac loaded in 29-31secs.


Perhaps you have an idea why there is this disparity in loading speed. It seems initialisation with the SATA SSD is a far simpler, smoother, process giving a 13 secs load time.


I wondered if the bad experience forcing the Adata NVME to work has had damaged the PCIE/Motherboard efficiency.

Any idea’s?

Jul 14, 2023 3:43 PM in response to HWTech

All most valuable information thank you HWTech.

It will take a week before I receive the new external SSD case so checking Adata health will take time.


Regarding Apple SSD, it is the original SM0128L and the Black Magic test in the previous post is perhaps suffering from Spotlight indexing activity. The test was done on the internal Apple SSD properly loaded via Recovery as you describe, but it has also been loaded with a number of applications and utilities used for system cleaning etc. The Account files were intentionally not transferred as a 128 disk is too small.


I have an external 1 TBSamsung T7 SSD with Ventura 13.3 and entire Account files. I also have TM volume on the same external T7 so I am covered for restoration options in case of difficulties such as those I have created. I also have a USB with bootable installation so have plenty of restoration options.


I have run the Apple hardware test on the iMac and received a clean bill of health as far as that test is concerned.


I ran DriveDX from external T7 and it confirmed 128Apple disk and the SATA SSD 100% OK and gave a life of 95% to the Apple SSD. Reassuring!


I very appreciate the time you have given and the care with which you describe correct procedure. Thank you for the good advice.



Jul 15, 2023 3:00 AM in response to HWTech

Ok HWTech,

the Ugreen External drive case arrived today and the 2TB Adata SX8600 is now loaded and connected via Lightning. It is a 10Gbps model max throughput. No software can reformat SX8600 as it cannot be mounted.


Perhaps the Adata can be mounted through the command line.


Drive Dx cannot recognise external drives neither Ventura on the Samsung T7 or Adata on the Ugreen external.



The iMac is running Monterey 12.6.7 downloaded from Apple Restore via Internet (Command R). Avira virus detection is switched off. Spotlight items are all un-ticked (unloaded). Other apps are Firefox, Disk Drill, Silent Knight, Onyx Black Magic, App Cleaner and music recording apps all of which were unopened.


  1. Mac registers SM2262 in Disk utility but cannot Erase, Restore or use First Aid.

2. Report from Smartmontools and Disk Utility.

3.Report Drive DX for Apple SM0128L.


  1. Drive DX results for Apple Disk SM0128L as attached:

Jul 15, 2023 5:49 PM in response to Australopithicus01

I don't see anything with the Apple SSD.


The external drive identified as "disk4" in the screenshots is only showing as 1GB in size (note the "G" instead of a "T"). If this is truly an SSD, then the SSD is bad, or you received a fake SSD which is unfortunately very common with online vendors with eBay and Amazon and I'm sure other community vendor sites as well. Or it could be due to a compatibility issue with the enclosure or adapters being used.



Jul 15, 2023 6:48 PM in response to HWTech

“I don’t see anything with the Apple SSD”


Hi HW Tech,

Does that mean you see nothing wrong with the Apple SSD? Seems to function OK.


I have not supplied Black Magic figures because if I start up from an external drive, Black Magic reads only the performance of the host drive. If I point Black Magic to the internal drive as you requested I receive a message saying, “Disk speed test cannot be run on the selected location because it is read only”. It seems I need to change disk permissions. I tried but found my usual method failed as a new security layer has been introduced. I shall have to work on that.


Disk 4, the Adata SX8600, (SM2262L) was registered as 2TB when originally installed. It was formatted and worked with my operating system of 200GB before I decided to erase the disc do to the intermittent boot-up behaviour.

The 1GB is a symptom of the problem with the Adata SSD. So far all evidence suggests it cannot be repaired because it cannot be mounted.


I do not understand the importance of your scrutiny of the Apple SSD. Does it potentially provide a clue to restoring the Adata SSD?




Jul 16, 2023 12:45 AM in response to HWTech

Hi HWTech,

I followed your directions and according to Terminal disk4 unmounted and the zero directions responded as you said. Then I tried Disk Utility First Aid which ran with a green tick. Previously I got red tick and a failure notice. Then I tried Erase but that failed again due to the unmounted issue. Then I ran First Aid again and got the red tick.


I repeated your directions again with Terminal and again, First Aid ran with green tick and operation successful. I have taken no further action pending your advice.

Jul 16, 2023 1:15 AM in response to Australopithicus01

Hi HWTech,

Regarding Apple NVME, you are quite right, I did complain the Apple NVME was slow taking over a minute to load 75GB. During our discussion I have run various tools to improve performance but it does take 57 seconds now to load that 75Gbs. The load procedure stalls at 17 secs. through initialisation then again at 37 secs. for about 20 secs. then races to the finish.


My mind has been dominated by the Adata SSD. I now recognise your concentration on the Apple drive is logical as any weaknesses will possibly apply to all NVME SSD. So it is an important issue.


Regarding the Adata drive, I followed your directions and according to Terminal, disk4 unmounted and the zero instruction code which behaved as you described. Then I tried Disk Utility First Aid which ran with a green tick. Previously I got red tick and a failure notice. Then I tried Erase but that failed again due to the unmounted issue. Then I ran First Aid again and got the red tick.


I repeated your directions again with Terminal and again, First Aid ran with green tick stating operation successful. I have taken no further action pending your advice.

Jul 19, 2023 6:14 AM in response to Australopithicus01

You provided incorrect drive identifiers which won't help. You need to provide the correct drive identifier for the physical drive which will be in the form "/dev/diskX" such as "/dev/disk4". You can get the correct drive identifier from the Disk Utility app. You will also need to add "sudo " to the beginning of the command since you need admin privileges to access the drive...if you don't either the utility will tell you or offer to authenticate (it has been a long time since I used TestDisk). I'm not sure if TestDisk has been updated with support for the new drive layouts or APFS file system.


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Can Bootup speed be improved Monterey 12.6.7

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