[Release] Resizable BAR BIOS EFI Module

Koekieezz · February 24, 2026, 2:42pm

@Vlad0 Try this: X79 Extreme4_Complete.rar (4.8 MB)

If you want the Intel ME FW to be updated in one go (stock FW from v3.70 is 8.1.40, i updated it to 8.1.70), i suggest you downgrade your bios if your current bios is version 3.70 (or L3.61 if you see it within windows dxdiag), then straight up update the bios as usual with instant flash.

To enable Above 4G Decoding (and Rebar, for later), you can refer to this post since the menu should be similiar. To confirm if Above 4G Decoding is working correctly, you can go to Device Manager → View → Resource by type → Large memory, and see the large memory range (if you’re not sure, you can send the Screenshot here):

Vlad0 · February 24, 2026, 9:23pm

I’ll try that bios Koekieezz, thanks.

Just to be clear on what I’ve tried I’ll post my process and maybe you guys can tell me where I went wrong.

Downloaded the latest bios from AsRock (3.70)
Insert ReBar.ffs using UEFITool 0.28.0 on the largest volume, right click the last file and choose “insert after this”, save.
I tried to then patch, created a patch folder and only let the patches.txt, UEFIPatch.exe and the Modded with ReBar.ffs bios, I did both the hover over and cd to the folder so I can see what’s happening, no matter if I patched a fresh non modded bios or the ReBar.ffs insert, I still got only one patch to work and it was 10Bytes. So I did not do the patches, which I think are only;
PciHostBridge | Replace 16GB MMIO region with complete use of 64GB PciBus | Don’t downgrade 64-bit BAR’s to 32-bit IvtOpianMrclnit | Extend MMIOH limit to fix Above 4G Decoding (X79), erased the # from this.
Open AMIBCP to unhide the PciSubsystemSetting’s folder and 4G
Opened HxD to copy my MAC.

Flashed my bios chip and booted using my old GPU, Enabled 4G( now available), disabled CSM (converted my os ssd to gpt) saved and exit bios, turned off pc before restart so I can swap the A380, booted and then I logged in. Saw that there was a Large Memory but set to PCI Express Root Complex under Resources by Connection. Tried to Install Drivers and I got a black screen, I Ctrl Shift Esc to run Explorer.exe and the screen was now normal, the installation hung, I ended it and saw that Device Manager now showed the 380 and not the generic display, but Code 43. So since I cannot get the patches to work I decided to use Clover to trick windows into thinking there’s space there for the A380 but I need “ReBarDxe.efi” and to redo my mod so that it doesn’t include the ReBar.ffs.

Another way is if I extract the snbQpianMrclnit PE3 body in UEFITool, save it as .efi, open it in HxD, look for 0F B7 96 42 01 00 00 and change it to 0F B7 96 00 20 00 00, apparently because I run an i7 3930 it can’t be InvtQpian. Then do the PciHostBridge, extract save to .efi and change that from 81 F9 00 00 00 04 TO 81 F9 00 00 00 10.

Open MMTool 4.50 and Replace the original modules with the edited ones in HxD, add my MAC and flash.

So do the 10byte mod using UEFIPatch, then extract and edit those two modules, replace them with MMTool, and flash.

Koekieezz · February 24, 2026, 9:46pm

@Vlad0 I think you’re missing one thing: DSDT Edit/Patch. This patch is a bit challenging if you never did DSDT/SSDT patch before, as this step is necessary to make the board able to allocate the MMIO to the cpu max supported Physical Address Size when above 4g decoding is initialized. You can examine yourself in the module AmiBoardInfo PE32 Body itself, the guide is there in the git page. Also a bit of advice, use UEFITool v0.25.0/v0.25.1 if you prefer to use uefitool method, as the latest v0.28.0 could cause pad file issues.

All in all, the shared bios i gave might be similiar to yours, but i did add Nvme boot mod, and i did update the microcodes, intel raid rom (both RST and RSTe EFI and OROM), Lan rom (both EFI and OROM), and the Intel ME Fw itself (as per mentioned before).

I don’t know any “Clover” method you use, but you can see on the post i mentioned above (in my 1st reply) where intel arc do work with this rebar mod, and this post which is another X79 chipset system.

If you have problem with intel arc, you can try this:

if you do have another gpu that is not the most recent gpu (say, like a gt 710, or gt 1030, or rx 460), use that gpu as it supports both UEFI and Legacy after flashing the bios i gave (wether you directly flash the bios with the most recent bios, or downgrade first then straight up instant flash the modded bios i gave)
boot up the system and go to bios, go to ACPI Option menu, find and disable “Launch CSM”, go to Pci Subsystem Settings, and enable Above 4G Decoding, then save and exit, go to bios again, and shut down the system (just press power button).
After system is off, replace the gpu with intel arc, and boot up normally, and install the latest driver for that gpu, it should work normally… unless the gpu have a hardware problem.

Vlad0 · February 25, 2026, 2:53am

If you were me and doing this mod, which steps would you take?

Based on what you read I’m familiar with, how would you go about it, I need a kinda guide from someone that knows more, I can follow instructions good enough, I made lots of mistakes in the last 9 days of me trying to do this, because I was not at all informed about bios, I read the GitHub the best I could. Just need a step by step guide I can follow, I’ll switch to the 0.25 version of UEFITools or you recommend another tool. I have my programmer from amazon, the cheap black one, I had to mod it so it outputs only 3.3v. I’ll go over the DSDT guide, just need a step by step, keep in mind the patches.txt file only contains the before mentioned patches and the only one that patches is a 10byte change so I’m guessing its the PciBus don’t downgrade to 32bit one.

Motherboard-X79 Extreme4

CPU-i7 3930K

GPU-Old:HD 7970 New A380

32Gigs of Ram

40TB Jellyfin Pool

Koekieezz · February 25, 2026, 10:02am

Did you flashed the bios i shared above or didn’t you? Or your board didn’t work from the mod that you have done previously?

The guide is there on github, and im not that good at explaining, so better off reading the git page, or try the bios i shared above and see the result.

Vlad0 · February 25, 2026, 6:12pm

Yes, I tried your bios, this is what happened;

Flashed with CH341A, needed to copy my Mac to your bios.

First try and the PC shut itself down, then turned on again and when I press F2 it started a ME update, then shutdown again. Started again then I could enter bios with my old GPU and made the changes, Enabled 4G, Disabled CSM ( I could not find a “Launch CSM” but I did find a regular CSM). Installed Drivers, black screen, code 43. I tried to change the ReBarEstate to 11, 10, 9, and no change, I know if I go to 8 I’ll get a motherboard code like b2 or b6 and the GPU won’t display and I have to do a clr cmos.

I was hopeful when I saw more menus on this bios, I also downloaded another bios you offered someone for x79 and 3.70 in another thread but that one didn’t work for me neither and had less options, like I said when I saw an OH Config folder and IMMOH settings set to 192G (or something high like that) I was hopeful.

Koekieezz · February 25, 2026, 7:27pm

I think Launch CSM was in ACPI, there is indeed a separate CSM menu, you can try to find this with amibcp or Uefi editor, and see where csm options are located on.

There is another way to confirm if system is running in pure uefi, which is by enabling secure boot, and install the secure boot keys (i think u do understand where it is and how to do it). So maybe, do a combination of CSM disable (just make sure when csm option is disabled, the other options below csm that tells which oprom to use would dissapear) + Above 4G Decoding + Secure Boot enabled + Keys installed. If your hd 7970 already supports pure uefi boot, i think it wont be a problem to try use it alongside with intel arc. Afterwards, just run rebardxe as admin and set it to 32, since i alrd set the default mmio to 128GiB, it should do more than 16GB bar with big ram installed just fine.

Also, after doing all of that, if u use windows, could you give a screenshot of Device Manager → View → Resource by type → Large memory?

Vlad0 · February 25, 2026, 9:03pm

I found 2 ACPI Folders, they have CSM Disabled, then I found another CSM folder in Boot, that wasn’t there before in my bios, and CSM is disabled there too and everything after CSM in that boot folder ( I think its called CSM Parameters) is set to Legacy. I clicked on everything in CSM Parameters and changed them to UEFI only, Enabled Secure Boot and installed keys. Typed 32 and still get a black screen after I log in, I have to run explorer.exe to be able to get the screen to normal, and still code 43. You didn’t tell me to turn all those options in CSM Parameters to UEFI only but I was trying to run pure UEFI, if its wrong I’ll turn them back. Got a picture like you asked , last time I checked the latency was 32, should that be 64 or more?

Koekieezz · February 25, 2026, 9:46pm

@Vlad0 I think it’s best to use the CSM option in the ACPI folder rather than in the Boot folder, basically just set CSM option in the ACPI folder, the one in Boot folder will automatically follow that.

There is no need to set that once CSM in ACPI folder is disabled, hence why i didn’t tell you about it, however, feel free to experiment with those if you feel it isn’t enough .

The screenshot you provided is correct, and Above 4G Decoding is functioning correctly!

If you want to read 2 cents of technical details why it works:
Large memory (Which is Above 4G Decoding) now sees and can use 64TiB of bar size if i was correct, based on the dsdt:

						CreateQWordField (CRS1, \_SB.PCI0._Y05._LEN, M2LN)  // _LEN: Length
						CreateQWordField (CRS1, \_SB.PCI0._Y05._MIN, M2MN)  // _MIN: Minimum Base Address
						CreateQWordField (CRS1, \_SB.PCI0._Y05._MAX, M2MX)  // _MAX: Maximum Base Address
						M2MX = 0x00003FFFFFFFFFFF
						M2MN = 0x0000380000000000
						M2LN = (M2MX - M2MN) + One

With 3FFFFFFFFFFF is 70368744177663 (512TiB) in decimal , and 380000000000 61572651155456 (448TiB) in decimal, and i assume your SNB/IVB max Physical Address is 46 Bit (2^46 = 70368744177663).

You can take a screenshot (assuming you used Prt Sc or Win + Shift + S) and ctrl + v in the comment block, you’ll get a full as-is screenshot btw!

As per why your gpu didn’t work, im guessing it is a hardware fault? HD7970 afaik, if you can boot it to uefi, could run rebar, GCN are able to run rebar with some registry hacks, as per what has been done on the X79 post i gave to you last reply.

Vlad0 · February 26, 2026, 3:09am

During this whole process I used the A380 except in the beginning because bios was set to legacy by default, I only used the HD 7970 once because it won’t work if CSM is disabled. Is your modded bios patched with the things my X79 Extreme4 needs or it just has everything unhid by AMIBCP? Do I still have to try and do my own DSDT patch, Don’t Downgrade to 32-bit patch, PciHostBridge change 16gig to 64gig patch and the Extend MMIOH limit patch? There’s nothing wrong with the motherboard as far as I know and the Intel ARC A380 is brand new never before opened, since you mentioned the mod not working maybe because of hardware fault. Or maybe I need to look into registry hacks to see if this will work.

MeatWar · February 26, 2026, 3:26am

Curious… such card works very…very well as UEFI boot/environment even on modern motherboards. Have you ever updated vbios/GOP driver…

Koekieezz · February 26, 2026, 3:44am

When i do gave, i do know what i did, unless i dont know, i will say that i dont know. Is the bios patched? Yes, you can check it yourself, and no, nothing need to be done in your end except figuring out if the A380 is malfunctioning in other system or not. The motherboard isn’t at fault, since you get image with HD 7970. It’s not the mod that isn’t working, it’s your gpu that might have a problem (since it got Code 43). Please re read what i’ve said before.

For the HD7970 able to run on pure uefi, you might need to mod/add uefi gop from this guide, or if you don’t know the how, you can post a screenshot of your gpuz with hd 7970 here (this mean you just turn the system to legacy for a while, remember to disable above 4g decoding and secure boot before turning csm back on.

Vlad0 · February 26, 2026, 5:28am

I’m new to anything that has to do with bios, that’s why its taken me over a week to figure things out a bit. I thought I could figure it out on my own, even if it took me a couple of days but my family uses the Jellyfin server and its been out of commission for a while, I was trying to get it to work with 4K eventually and also for the cheapest I could afford and the A310 came up in chats. The A310 is hard to come by because the version I wanted, sparkle elf, although less powerful than the A380 does not require to be plugged in to get more power, it gets all its power from the PCIE rail and only uses 50W-75W, unlike my AMD Radeon HD 7970, that can use up to 250W and it can only work with 1080p and still struggles a bit with that. This Tower used to be my gaming PC from 13 years ago, now that it cannot run a lot of games and I have a gaming laptop I decided to turn it into a Jellyfin server but only if I can do it for very little money. I read about this mod and also that NVIDIA cards don’t need ReBar or Above 4G Encoding and can work on my board but cards that I would need like the RTX 4060 are now around $400-$600 and other like the RTX 5060 are cheaper but still not cheaper than the A310 or A380, so….I decided on the A380.

Vlad0 · February 26, 2026, 5:40am

Thanks for sharing your Mod with me, I learned something new from this chats, this might just be that I have the wrong drivers, I run Win10Pro and the drivers I tried to installed are this; gfx_win_101.8425_101.8362.exe, I used DDU so its not a conflict of ghost AMD drivers either, it could also be that this mod, with this board and this GPU doesn’t work. After I look into the drivers maybe being the cause of the mod not working and I still get code 43, then the experiment is done and I will start looking at NVIDIA cards like the 4060 to be my Jellyfin transcoder.

Zaver · February 26, 2026, 6:10am

Hello!
AMD Radeon HD 7970 is also old, its BIOS may or may not contain UEFI, depending on the firmware version.
A large database of video adapter BIOSes can be found here

I have a dinosaur T-Rex Radeon R7 350 (Oland, GCN1) contains UEFI and works with ReBar, but there are many surprises and there is no performance gain.
On the contrary, I have a newer motherboard and a T-Rex video accelerator/
The A380 video accelerator should work perfectly with ReBar/
Thanks/

Vlad0 · February 26, 2026, 7:19am

My problem was not the HD 7970, I know its old but if you know a few tricks you can still squeeze some life out of it as a basic Jellyfin transcoder. The only problem is it can only do 1080p, which is fine but if I ever move to something higher or H265, AV1 4K, then my 7970 cannot do anything about that, I am aware. The Problem was making my new Intel ARC A380 GPU work on my old X79 Extreme4 Motherboard. It would require a ReBar and Above 4G Encoding bios mod but it would be able to work, in theory. Since I have almost $0 for this project, I either stay with my limited 7970 as my main transcoder for Jellyfin, I would have to change my ssd back to MBR, get a fresh 3.70 bios and add my Mac and I’m back where I started or somehow this mod works and I keep the A380 and all is well or buy a cheap Rebar-Above 4G Encoding native motherboard, buy a cheap GPU and also ddr4 ram and use the A380 with that or buy a NVIDIA card, I read are backwards compatible with PCIe 3.0 don’t require ReBar or Above 4G encoding and might work well with my old board.

Zaver · February 26, 2026, 8:42am

What about Win11?

Everything works for me on Win 11/

Thanks/

Koekieezz · February 26, 2026, 9:50am

@Vlad0 It is indeed not the problem, but if you could get the 7970 flashed with uefi gop vbios, you can get rebar running (since you already used rebarstate at 32), and with registry hack for polaris, you can get the amd driver running rebar on that gcn, this is the 1st step to see if rebar is working well.

I don’t know why did you keep insist that the mod didn’t work, as per what you’ve explained in the forum before, even before modding the bios, the A380 didn’t work, and you didn’t explain us further if the A380 works on another system (no Code 43).

Code 43 is common for HW init failure, which in this case the gpu is failing, either that it physically failing OR the firmware is failing. IF the mod causes code 43, wouldn’t it also cause code 43 with HD 7970? I think you should crosscheck by flashing an UEFI Gop vbios for your HD 7970 (which why i asked gpu-z screenshot of your HD 7970), and i could help with flashing the 7970 to support full uefi, and you can proceed to activate rebar for gcn with the polaris rebar legacy registry hack (it’s well documented in guru3d forum), and confirm that rebar worked correctly.

I also did gave you a bit of explanation that above 4g decoding worked since the bios now mapped large MMIO space from 448TiB up to 512TiB (total 64TiB) right? This mean, the modded bios do work, and also this is not the 1st time i did the mod, but it’s a good thing to not trust someone online like me, you can see in my profile → created topics by me, that i did some rebar mods along with other firmware updates, to answer your question if i did everything accordingly

AFAIK, Rebar, is supported ever since PCIE 2.0/2.1. You can see the Z77 Extreme4/9 post i did, that the user that tested my made mod have it working on sandy bridge cpu.

Feel free to discuss it here if you have any more questions, and yes i didn’t use AI to generate my reply comment (you can totally see some broken grammar i did ). Btw, thank you for testing @Vlad0 !!

Vlad0 · February 26, 2026, 7:19pm

No more black screen

I had the ReBarEstate.exe to 11 that’s why you see BAR0 2048MB, everything seems to work, it turns out it was the latest drivers that were detecting the mod and stopping it. I looked for the oldest I can find, 101.4644, and it worked. Little concerned that the GPU is not working on anything right now and its already at 46 degrees and the fan is not turning on, the Intel ARC control showed a “ReBar is available but not enabled” message after restart but the GPU-Z says otherwise.

Koekieezz · February 26, 2026, 7:21pm

@Vlad0 is this on another system or still on the same system? How did you manage to get it to work? Have you tried to set it with rebarstate at 32 instead (and after you reboot after setting it to 32, check Device Manager → View → Resource by type → Large memory)