iMac Retina 5K 27" 2020: SD card reader issue

There are some reports that Sonoma has a problem with FAT32 and exFAT formats.

see > Files are corrupted when copying to FAT32… - Apple Community

and > SSD not mountable on Sonoma 14.0 - Apple Community

If you are only using those SD card(s) and/or other external drives to move data between the two iMac's..?

Then you should use Disk Utility to format those SD cards and external drives to a Mac friendly format.

see > Initialize a external storage device in Disk Utility on Mac - Apple Support

Hello,

rFlight It's possible that the issue you're experiencing is related to the SD card reader on your iMac or compatibility issues with the SD card itself. Here are a few troubleshooting steps you can try to narrow down the cause:

1. Check SD Card Compatibility: Ensure that the SD card you're using is compatible with your iMac's SD card reader. Some SD cards may have compatibility issues with certain card readers or operating systems.
2. Try a Different SD Card: Test the SD card reader with a different SD card to see if the issue persists. If another SD card works fine, the problem may be specific to the original SD card.
3. Check for Software Updates: Make sure your iMac's operating system and any related drivers are up to date. Sometimes, software updates can fix compatibility issues or bugs related to hardware components.
4. Reset SMC and NVRAM: Resetting the System Management Controller (SMC) and Non-Volatile Random Access Memory (NVRAM) on your iMac can sometimes resolve hardware-related issues. Instructions for resetting these components can be found on Apple's support website.
5. Verify File System Integrity: Use Disk Utility to verify the integrity of the file system on the SD card. It's possible that there may be file system errors causing the incorrect display of available space.

rFlight wrote:

My iMac has issues with certain SD cards. It reads all files on the card perfectly but shows 0 bytes left. I therefore am unable to add new files to the card (Finder says card full) although it acutally is almost empty. Getting the card info (⌘I) shows 0 bytes for all entries. It's a FAT32 formatted card that I use on another system. A reboot usually fixed the problem but only for a few inserts and ejects.

My old iMac 27" late 2015 running Monterey 12.7.4 reads the card without issue and displays the free space correctly every single time.

Is this a known problem with Sonoma or is my SD card reader the issue?

If you have deleted files from the SD card(s)..?

Then you need to Empty the iMac's Trash in order to free up that space on the SD card(s).

It's possible that the issue you're experiencing with the SD card reader on your iMac Retina 5K 27" 2020 model is related to compatibility or software settings rather than a hardware problem.

You're welcome.

Yea' that sounds like a workable solution.

Agreed.

It might help to send feedback.

Feedback - macOS - Apple

Feedback - iMac - Apple