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Reply To: [Solved] Thunderbolt 4 SSD Speeds Throttled to USB 3.0 on MacBook Pro 16″ M2 Max: How to resolve Passive cable PCIe link negotiation falling back to USB 3.2 Gen 2
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Terry GrayVerifying certified 40Gbps active cables, resetting Thunderbolt kernel extensions, and enabling TRIM.
Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:
- Verify cable has official Thunderbolt 4 lightning bolt and ‘4’ logo. Charging cables will not negotiate PCIe.
- Reset bus enumeration:
sudo killall -9 diskarbitrationd. - Enable APFS TRIM support:
sudo trimforce enable.
Following this procedure restores full stability with zero recurring log errors.