Z390 Phantom Gaming 4S/ac BIOS CROSSFLASH Resizable BAR

I wonder if there is any diference on the original 4S non AC compared to 4S only bios, but also this experiment means that you could keep the board bios up to date!

i remember vaguely but on 2021, on reddit a redditor have a complaint about this but not rebar, more to latest bios. i have a tought about “maybe flash the bios region of original counterpart would work, overriding 4S bios with 4S/ac board since they’re identical” and the rest is just a tought/theory to me :stuck_out_tongue:

Idk what gpu you are on but if your gpu is 8GB then it should be 8GB, working as intended :smiley:

*since your board does have an AC Wifi module did it still work?

Everything is identical. Between both boards, the only difference appears to be that one was OEM so it came in a “pre-built” maybe like “bare-bone system” I am not sure how they sold it, but the one I bought, came with a m.2 ac wifi card, but I replaced it with a better one that that uses the AX protocol of wifi6, then I just use “intel driver update assistant” and it works fine.
the layout of everything is absolutely identical. I dont know why ASrock would lock the bios like that. No reason at all…

I have the latest bios now, and this is now an unsupported platform so, no new bios will be coming out for it anyway. but this clever access memory is all I cared about.

Yes I have the AMD 5700XT which comes with 8GB vram, I did not know that the re-BAR was meant to simply match the VRAM amount, makes sense now that I think about it.

Here is the OEM board

Here is the Retail board


Yeah i forgot to tell about you that on asrock it is sometimes called C.A.M instead of regular rebar, as far as i remember on b450 and b550 build that i built for my friend it is still called rebar… maybe got bad memory about it XD

And yeah, rebar always meant to match your vram, since thats how much the cpu could access the vram directly.

Hi!! Can someone upload the 1.40 version modified? Thank u :smiley:

no need modified bios for it i guess, you could just flash (or crossflash if your mobo is 4S/ac ver) version 1.40C version. disable CSM and find resizable bar option, enable it, and find Clever Access Memory option and enable it.

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Yes, Koekieezz is right, he gave me the idea of using the FPT64.exe program, but I am the one that actually has the motherboard in question, and performed the modification, and I am want to verify what he said and say that there is no BIOS modding involved when you flash the 1.40C into the 4S/AC version, hence why we refer to this process as “crossflashing” throughout the thread.

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Are there any videos or could you guys explain the process of crossflashing to a beginner.

@Nemesis read this and the image bobby sent. it pretty much sums it all, or better, read the entire post.

So to cross flash I would need to use Gpreset using Intel gpt first? Then just put the bios 1.40c ?

to flash, use this args: -f rom name -bios, after it succeed, do this arg: -greset

Some of the BIOS downloads from ASRock include a GUI flasher. AFUWINGUIx64.EXE

1.30 should have it included.

Also available from AMI directly here.

Hello, could you pass the version of the bios modified with the mod of the rezisable bar 8 GB

you could just crossflash latest Phantom Gaming 4S bios instead of getting a bios mod.

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I changed the title of the topic and I removed the word “mod” because people just read the title. I replaced it with the word “crossflash”. The thread may or may not be harder to search for but at least people that find it may not be asking around for a mod anymore since its not really necessary. Maybe this thread should be locked or marked as “resolved”.
The more people keep asking for mods, the harder it will be to find the important information in it.

Maybe a cleaner guide could be written because the way the thread is laid out with all the questions is probably very confusing. I am also guessing people are confused about how to use the command prompt, but unless they ask specific questions about that it is hard to help them.

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Thank you for posting this! I just successfully “force”-flashed the bios (with the latest 4.40I [Beta] version available here on my Aliexpress “Z390 Phantom Gaming 4/ac” motherboard that had bios P1.00 previously.

This was a “4/ac” according to the bios, not the “4S/ac” version that I’ve seen was shipped by OEMs, so none of the various OEM-provided bioses on Reddit etc. worked. I can’t find any reference to the 4/ac version of this motherboard anywhere, so perhaps a pre-release, or region-specific board.

I flashed using the EFI shell version of FPT (available here) on a USB drive after doing a backup dump, i.e.:

FPT -bios -d backup.bin
FPT -bios -f Z39PG4_4.40I
FPT -greset

I then when back into the new bios and used the Instant Flash tool to flash Z39PG4_4.40I again for good measure. All working great now, and reporting the retail bios version.


For your information,

You own an iBuyPower Z390 Phantom Gaming 4 IB the latest firmware for it is Z39PGIB_4.33 located here:


The AliExpress sales people put AC instead of IB, but the correct name ends in IB.

AsRock has a page dedicated to some OEM BIOS, but is not very well updated:
However, this AsRock page does contain a picture of the 4 IB and it looks identical to that AliExpress stuff that is misnamed as 4 AC (notice the rectangular chipset heatsink instead of a triangular one seen in 4S variants)

The only difference is that this OEM board comes with the wifi module whereas the original does not. It is important to note that it is unlikely that the bios on this iBuyPower website supports reBAR/CAM.
Because iBuyPower abandoned supporting these products a long time ago.

So the moral of the story is that you cross-flashed the correct BIOS, congratulations. The motherboards are absolutely identical! And you didn’t miss out on anything by not finding this iBuyPower crap site.

As long as the motherboard looks the same int he pictures, that is the main thing