NVMeFix is a set of patches for the Apple NVMe storage driver, IONVMeFamily. Its goal is to improve compatibility with non-Apple SSDs. It may be used both on Apple and non-Apple computers.
The following features are implemented:
- Autonomous Power State Transition to reduce idle power consumption of the controller.
- Host-driver active power state management.
Other incompatibilities with third-party SSDs may be addressed provided enough information is submitted to the bugtracker.
Unfortunately, some issues cannot be fixed purely by a kernel-side driver. For example, MacBookPro 11,1 EFI includes an old version of NVMHCI DXE driver that causes a hang when resuming from hibernaton with full disk encryption on.
NVMeFix requires at least Lilu 1.4.1 and at least 10.14 system version. It may be compatible with older systems, but has not been tested.
It may be installed to
/Library/Extensions, or injected by the bootloader.
-nvmefdbg enables detailed logging for
-nvmefoff disables the kext.
Some SSDs misbehave when APST is on. NVMeFix attempts to detect broken motherboard and SSD combinations and work around them. Motherboard is detected via IORegistry keys injected by Clover, or NVRAM variables provided by OpenCore.
APST table entries specify minimum idle latency for the transition to occur. Maximum acceptable
latency is 100000 microseconds, and may be overriden via little-endian 8-byte property
ps-max-latency-us of parent PCI device (e.g.
IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/RP06@1C,5/IOPP/SSD0@0). If set to 0, APST
will be disabled completely.
Note: IOKit message
Couldn't alloc class "NVMeFix" is not an error.
RELEASE build will only log high-level information about failures.
DEBUG build will additionally log used power states, detailed error messages, and attempt to
fetch APST status and table from the controller.
APST enable status is posted to the IONVMeController IORegistry entry
If active power management initialisation is successful, an
NVMePMProxy entry will be created
in the IOPower IORegistry plane with IOPowerManagement dictionary.
Information about power states supported by the controller may be obtained e.g. using
For example, in the following output the controller reports 5 states, where the former three
high-power states will be used by NVMeFix for active power management, and the latter two may be
used for APST depending on
Supported Power States St Op Max Active Idle RL RT WL WT Ent_Lat Ex_Lat 0 + 9.00W - - 0 0 0 0 0 0 1 + 4.60W - - 1 1 1 1 0 0 2 + 3.80W - - 2 2 2 2 0 0 3 - 0.0450W - - 3 3 3 3 2000 2000 4 - 0.0040W - - 4 4 4 4 6000 8000