IFR Extractor How to interpret variables

[pepitillo]

Hello,

I was playing with an old Asus Sandy Bridge laptop with UEFI and tying to boot Mojave (BTW High Sierra leads to some boot errors).

 

The installer won't boot because the USB it's not recognized.

 

I've done a little bit of research playing with BIOS image and UEFITool, AMIBCP and IFR Extractor. 

I've realized that EHCI HandOff is Off by default, and I know it's necessary to boot from USB on macOS.

 

On IFR txt I have :

 

Variable Store Select: 0xF000 {25 04 00 F0}
0x24428 																																			Variable 0x0[1] equals 0x1 {12 07 00 00 01 01 00}
0x2442F 																																				Variable Store Select: 0x3C {25 04 3C 00}
0x24433 																																				Setting: EHCI Hand-off, Variable: 0x2[1] {05 09 02 00 01 84 04 85 04}
0x2443C 																																					Option: Disabled, Value: 0x0 {09 09 7C 04 00 00 13 00 00}
0x24445 																																					Option: Enabled, Value: 0x1 {09 09 7B 04 01 00 10 00 00}
0x2444E 																																				End of Options {10 02}
0x24450 																																			End If0x24450 																																		End If {18 02}
0x24452 																																		Subtitle:  {02 04 02 00}

But changing variable 0x2 changes something from UEFI Boot.

 

Can someone explain me how to interpret this ? 

There's something to do with the Variable Store Select 0x3C ?

 

I attach my whole IFR tables file.

 

Thanks 

Setup.txt

Edited February 14, 2021 by pepitillo