I can confirm both the slot 5 (x16) and 7 (x16) work for x4x4x4x4 burification after testing. Thanks!
open the bios.CAP with UEFITool, save the UEFI part as image.rom.
open image.rom with AMIBCP 5, change the option you want, save.
in HxD open both the original bios.CAP and the modded image.rom
select the first 800h bytes of the bios.CAP (capsule header) and insert this block at index 0 of image.rom, save as Z10PEWS.CAP
use ASUS backflash (checksums of the CAP header doesn't match the bios because fof the mod)
if you know the index of the vaiable, you can change the bufurcation option direct with HxD
result of Universal IFR Extractor (how to get this, check the howto in ASUS_Z10PE-D8_BiosModding_Tools)
Code:
0x1B2F1 Form: IIO 1, Form ID: 0x77 {01 86 77 00 86 04}
0x1B2F7 Suppress If: {0A 82}
0x1B2F9 Variable 0x212 equals 0x0 {12 06 12 02 00 00}
0x1B2FF Setting: IOU2 (IIO PCIe Port 1), Variable: 0x552 {05 91 C6 04 D1 04 5E 02 01 00 52 05 10 10 00 FF 00}
0x1B310 Option: x4x4, Value: 0x0 {09 07 D6 04 00 00 00}
0x1B317 Option: x8, Value: 0x1 {09 07 4F 0A 30 00 01}
0x1B31E Option: Auto, Value: 0xFF {09 07 80 03 00 00 FF}
0x1B325 End of Options {29 02}
0x1B327 Setting: IOU0 (IIO PCIe Port 2), Variable: 0x54A {05 91 CA 04 D1 04 5F 02 01 00 4A 05 10 10 00 FF 00}
0x1B338 Option: x4x4x4x4, Value: 0x0 {09 07 D2 04 00 00 00}
0x1B33F Option: x4x4x8, Value: 0x1 {09 07 D3 04 00 00 01}
0x1B346 Option: x8x4x4, Value: 0x2 {09 07 D4 04 00 00 02}
0x1B34D Option: x8x8, Value: 0x3 {09 07 D5 04 00 00 03}
0x1B354 Option: x16, Value: 0x4 {09 07 50 0A 30 00 04}
0x1B35B Option: Auto, Value: 0xFF {09 07 80 03 00 00 FF}
0x1B362 End of Options {29 02}
0x1B364 Setting: IOU1 (IIO PCIe Port 3), Variable: 0x54E {05 91 CE 04 D1 04 60 02 01 00 4E 05 10 10 00 FF 00}
0x1B375 Option: x4x4x4x4, Value: 0x0 {09 07 D2 04 00 00 00}
0x1B37C Option: x4x4x8, Value: 0x1 {09 07 D3 04 00 00 01}
0x1B383 Option: x8x4x4, Value: 0x2 {09 07 D4 04 00 00 02}
0x1B38A Option: x8x8, Value: 0x3 {09 07 D5 04 00 00 03}
0x1B391 Option: x16, Value: 0x4 {09 07 50 0A 30 00 04}
0x1B398 Option: Auto, Value: 0xFF {09 07 80 03 00 00 FF}
0x1B39F End of Options {29 02}
0x1B3A1 End If {29 02}
IOU0 (IIO PCIe Port 2), Variable:
0x54A
IOU1 (IIO PCIe Port 3), Variable:
0x54E
open the original bios.CAP in HxD
search for "intelSetup" (Varstore of the IntelRCSetup)
"IntelSetup" is zero terminated string. select the following 00
open select block function
nr.of bytes is the index of the option you want to change, in this case: IOU0 (IIO PCIe Port 2), Variable:
0x54A
the last selected bytes is the option, here 0x4 the default of orig. bios. what this means ? check the result of Universal IFR Extractor
Option: x4x4x4x4, Value: 0x0 {09 07 D2 04 00 00 00}
Option: x4x4x8, Value: 0x1 {09 07 D3 04 00 00 01}
Option: x8x4x4, Value: 0x2 {09 07 D4 04 00 00 02}
Option: x8x8, Value: 0x3 {09 07 D5 04 00 00 03}
Option: x16, Value: 0x4 {09 07 50 0A 30 00 04}
Option: Auto, Value: 0xFF {09 07 80 03 00 00 FF}
just set to 0x0 for x4x4x4x4