Z390 Phantom Gaming 4S/ac BIOS mod for Resizable BAR

Hello I bought an OEM motherboard at a store it is technically identical to the ASRock Z390 Phantom Gaming 4S, but the version I have is called Z390 Phantom Gaming 4S/ac, and it was pulled out of OEM iBuyPower Systems.

The latest BIOS from iBuyPower is “Z39G4SA_1.21A”, but the latest non-OEM BIOS is “Z39PG4S1.40C (beta)” at ASRock’s website, and it contains the Resizable BAR, AKA “ASRock Clever Access Memory” update for AMD graphics cards.

When I try to flash the 1.40C non-OEM BIOS, the Instant-Flash utility will not detect the file. So I am stuck at the OEM “1.21A” BIOS which does not contain the Resizable-BAR/“Clever Access Memory” update.

Can somebody help me transfer all the good stuff of the 1.40C BIOS into the locked OEM 1.21A?, or Maybe help me “change the identity” of my motherboard so that I can upgrade straight up to 1.40C, or maybe just modify the OEM 1.21A BIOS so that it has the new micro-code and Re-BAR.

If possible however, I’d rather have everything from the 1.40C BIOS including its interface/GUI, so that I have a toggle for Re-BAR and all the the other goodies.

This is purely a software lock. Both motherboards are absolutely identical.
Has anybody else tried messing around with these motherboards for this purpose? Can anybody help me do this mod? I have attached both BIOS files.

Z390 Phantom Gaming 4S(1.40C)ROM.zip (9.8 MB)
Z39G4SA_1.21A.zip (9.7 MB)

Some users had success in cross flashing similar bios in other brands/models motherboards…
You can try programming Asrock bios with a CH341 with a clipper or via the SPI_TPM_J1 header.
The “fusion” of the 2 is usually not possible… my opinion only.
Another option…maybe… replacing the iBuyPower Intel_image region bios, with the Asrock one.
UEFI tool can be used for this.

There’s no certain of success in any of this options.

All this off course has its own RISKS of failure operation and several backups should be made to recover the motherboard.

1 Like

Can anybody verify that this worked? Has anybody tried this (cross-flashing) on this board?

@MeatWar Do you know if all of this software lock stuff is in the BIOS itself? I am not sure how this motherboard ID system works. So for example, if I cross-flash using the clip, then, the motherboard will (in theory) adopt the new ID right?

I dont understand how the motherboard “knows” that a new BIOS update will be compatible or not, and therefore block the upgrade. I assume it is some type of ID number or something.

What about just modding the OEM “1.21A” BIOS with resizable BAR? Can anybody help me with that since this is a request forum?
Are there any generic tutorials for me to DIY it? I am getting a bit lost in the forum here.