Migrating from a Late-2015 iMac to an M4 Pro MacBook Pro

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Migrating from a Late-2015 iMac to an M4 Pro MacBook Pro

Hi all. I have a fairly complicated problem which I hope will have a simple solution. I've just bought a brand new M4 Pro MacBook Pro to replace my ancient iMac (late-2015, i7, 27-inch).

I'd like to migrate all of my data (approx. 2TB) from this old iMac to my new MacBook, but I keep finding conflicting information online on the best way to do this. I understand that using a Time Machine backup to migrate is the most efficient method, however today I ran into a big problem...

Online guides have recommended I update my old iMac to the newest possible OS before migrating, so I updated to Monterey. I've just attempted a Time Machine backup for the first time since this update but the backup stalled at around 38% and stayed like that for about 5 hours, so I eventually stopped the backup.

So now I'm not sure what to do. I could re-attempt the backup but if that is unsuccessful again I need the next best alternative for migrating my data from my iMac onto my new MacBook. So far I've found all sorts of conflicting information online and Apple Support articles don't seem to help since this seems to be an unusual problem.

As far as I know I can't migrate via Thunderbolt cable as my iMac only has Thunderbolt-2 ports. And I'd rather avoid WiFi as I've heard it will take far too long and it isn't very reliable.

Can anyone offer some rock solid solutions? Thanks in advance.

Posted on Jun 9, 2025 8:21 AM

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Answer 1

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Servant of Cats

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Jun 10, 2025 6:16 AM in response to hugh222

hugh222 wrote:

As far as I know I can't migrate via Thunderbolt cable as my iMac only has Thunderbolt-2 ports.

You could – but it would be expensive. You'd need to get a $50 Apple Thunderbolt 3-to-2 adapter and a $30+ Thunderbolt 1/2 cable (the last might be difficult to find). You'd probably only use that equipment one time.

It would be better to put that money towards buying a new external drive that is large enough to use for backup purposes. Then you could make a Time Machine or bootable clone (CCC, SuperDuper!) backup of the old Mac. After the new Mac had successfully migrated from the backup, you could erase the drive, and reuse it to make a backup of the new Mac.

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Answer 2

Old Toad

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215,094 points

Jun 9, 2025 10:59 AM in response to hugh222

Another way you can do it is to connect the two Macs via Ethernet cable and when you first boot up your new MBP at some point you'll be asked to select your old Mac or Time Machine drive or PC.

Then you'll be asked what data to migrate over to your new MBP:

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Answer 3

rkaufmann87

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148,422 points

Jun 9, 2025 8:44 AM in response to hugh222

First be patient! Your problem is not difficult, simply replace the External Hard Disk you are using for Time Machine as it may be old and in poor condition. Old would be anything about 5 years or older, especially is you bought a Walmart quality enclosure which tend to overheat. Replace with a high quality and reasonably priced External Hard Disk such as the OWC Mercury Elite Pro . I would recommend the 4TB version for your needs. Then once you have backed up the 2015 execute the instructions per Setup Assistant and Migration Assistant.

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Answer 4

hugh222 Author

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Jun 9, 2025 9:06 AM in response to rkaufmann87

Thanks for your advice rkaufmann87. I hadn't had any problems with my external HDD prior to updating to Monterey. But yes it is quite an old WD My Book for Mac so it's probably about time I replaced it anyway.

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Answer 5

hugh222 Author

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Jun 10, 2025 1:05 AM in response to Old Toad

Thanks Old Toad. If I don't have any luck with the Time Machine method I'll certainly give that a try.

Given that my MBP doesn't have an ethernet port, I assume Apple's ethernet-to-USB-C adapter will do the job? I'm fairly sure I've got one lying around somewhere.

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Answer 6

hugh222 Author

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Jun 10, 2025 8:43 AM in response to Servant of Cats

Thanks Servant of Cats that all sounds very sensible. I'll treat the old Thunderbolt option as a last resort, but hopefully I won't need it!

Re external HDDs, the OWC Mercury Elite Pro that rkaufmann87 recommended isn't widely available here in the UK so I'll see if I can find a similar alternative.

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Answer 7

rkaufmann87

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Jun 10, 2025 9:16 AM in response to hugh222

Actually it should be widely available in the UK, first try Amazon and if they don't have it on www.macsales.com they have a link for UK (and other nations) distributors. You shouldn't have too much problem getting them where you live.

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