Enable P2SB device on ASRock Z170 Extreme4+

I’m trying to enable the P2SB device on the “ASRock Z170 Extreme4+” motherboard but it seems not to work.

My CPU (it should support P2SB):
processor : 7
vendor_id : GenuineIntel
cpu family : 6
model : 94
model name : Intel(R) Core™ i7-6700K CPU @ 4.00GHz

That’s the way I’m trying to get it enabled:

1. Downloading the bios

2. Using UBU v1.65.6 to remove the ASRock protection
- I’m just loading and saving the BIOS without any modification of the embedded drivers

3. Modifying the BIOS options with AMIBCP v5.02.0023
- Look for the entry “Unlock PCH P2SB” in “Empty Folder”->Setup->PCH-IO Configuration>
- Set the “Failsafe” and “Optimal” option to “Enabled”
- Modify a visual BIOS option string in “BIOS Strings” to verify that the modified BIOS is flashed properly
- Save modified BIOS

4. Flash the modified BIOS with the “instant flash” function from the current BIOS
- Verify that the modified BIOS string is visible after reboot

5. Restore default BIOS options by pressing F9

6. Save settings and boot to OS
=> P2SB device should be visible now

Any idea what I could have done wrong or what I’m missing here ?