# Fixing System Clocks on HEDT: Manual
# Seeing if you need SSDT-RTC0-RANGE
To start, first open your decompiled DSDT you got from Dumping the DSDT and Decompiling and Compiling with either MaciASL(if in macOS) or any other text editor if in Windows or Linux(VSCode has an ACPI extension (opens new window) that can also help).
Now search for PNP0B00
and look at the _CRS
entry within it:
And from the above example, we see we have 2 banks of RTC memory:
- Bank 1: starts at 0x70 and is length 0x2
- Bank 2: starts at 0x74 and is length 0x4
Now the problem is that the OEM forgot to mat sections 0x72 and 0x73. Because of this, macOS may halt while booting(prominently in Big Sur)
And finally, verify if it has an _STA method as well. This will be used shortly
# Finding the ACPI path
Finding the ACPI pathing is quite easy actually, first open your decompiled DSDT you got from Dumping the DSDT and Decompiling and Compiling with either MaciASL(if in macOS) or any other text editor if in Windows or Linux(VSCode has an ACPI extension (opens new window) that can also help).
To start, search for the following:
- Finding the RTC name:
- Search
PNP0B00
- Search
- Finding the LowPinCount path:
- Search
Name (_ADR, 0x001F0000)
- Search
- Finding the PCI path:
- Search
PNP0A08
(If multiple show up, use the first one)
- Search
You should get something like the following show up:
RTC Pathing | LPC Pathing | PCI Pathing |
---|---|---|
From the above, we can see we have RTC
, LPC0
and PCI0
. Now we can head to the next stage
# Edits to the sample SSDT
Now that we have our ACPI path, lets grab our SSDT and get to work:
By default, this uses PC00.LPC0.RTC
for the pathing. you'll want to rename accordingly.
Following the example from above, we'll be renaming it to PCI0.LPC0.RTC
:
Before:
External (_SB_.PC00.LPC0, DeviceObj) <- Rename this
External (_SB_.PC00.LPC0.RTC_, DeviceObj) <- Rename this
Scope (_SB.PC00.LPC0) <- Rename this
Following the example pathing we found, the SSDT should look something like this:
After:
External (_SB_.PCI0.LPC0, DeviceObj) <- Renamed
Scope (_SB.PCI0.LPC0.RTC) <- Renamed
Scope (_SB.PCI0.LPC0) <- Renamed
/* <- Remove if your RTC device didn't have an _STA
Scope (RTC)
{
Method (_STA, 0, NotSerialized) // _STA: Status
{
If (_OSI ("Darwin"))
{
Return (Zero)
}
Else
{
Return (0x0F)
}
}
}
*/ <- Remove if your RTC device didn't have an _STA
# Compiling the SSDT
With the SSDT done, you're now ready to compile the SSDT!
# Wrapping up
Once you're done making your SSDT, either head to the next page to finish the rest of the SSDTs or head here if you're ready to wrap up: