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OS 10.14.5 does not support 128GB SD cards

I bought a 128GB SD card (SanDisk Extreme Pro SDXC UHS-1). Its filesystem is ExFAT.


I have a iMac Retina 5K, 27-inch, 2017 running Mac OS 10.14.5. When I insert the card in my iMac's card reader it won't mount. The card shows up in Disk Utility but I can't mount it from there either. I have reseted SMC and then I was able to mount the card for a day. The next day (today) Mac OS 10.14.5 started to refuse to mount it again. I reseted SMC again, but this time it didn't help.


The 128GB card works fine in my camera AND the card mounts perfectly on my Macbook Pro (late 2009) where I'm running Mac OS 10.11.6. So the card is not defect.


I also have two 32GB SD cards, and I can mount both of these cards on my iMac 10.14.5 without any problems. So I know that there is no hardware problem with the card reader in my iMac since I'm able to mount my 32GB SD cards on it.


The issue is that Mac OS 10.14.5 can't mount a 128GB SD card. Mac OS 10.11.6 can. So it must be a software bug in OS 10.14.5.


Any chance that Apple will fix this? Are they aware of this bug?

iMac 27" 5K, macOS 10.14

Posted on Jul 9, 2019 1:01 PM

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Posted on Jul 9, 2019 1:52 PM

Did you try rebooting?


Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379


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OS 10.14.5 does not support 128GB SD cards

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