[Problem] No LEGACY Boot Mode on Lenovo Legion 15ACH6

BIOS/UEFI Modding BIOS Modding Guides and Problems
1

Hello *.*!

First time poster here, hoping to find some help on the following issue:

I have two Legion 5 laptops here:

A: 15ACH6, AMD with 3070 GPU, BIOS GKCN65WW, with Bios Boot menu without “Boot Mode: Uefi | Legacy” and no “Boot Priority: UEFI First | Legacy First”. Only NVMe drives are possible in this machine.

B: 15IMH05, Intel with 1660 GPU, BIOS EFCN48WW, where the Boot menus are visible and selectable. This laptop can be equipped with SATA and NVMe drives.

My goal is to try installing Windows 7 on A for learning purposes and curiosity, no big use case behind that idea. In order to manage that I want to somehow enable the BIOS boot legacy option.

What I already tried out:
The BIOS of A is decomposed and I have the IFR files for the SetupUtility, where file 6.2. is containing the parts

Form FormId: 0x1, Title: “Boot” { 01 86 01 00 C2 00 }
0x65117: Subtitle Prompt: " ", Help: “”, Flags: 0x0 { 02 87 7A 00 00 00 00 }
0x6511E: End { 29 02 }
0x65120: GrayOutIf { 19 82 }
0x65122: EqIdValList QuestionId: 0x2, Values: [2, 3] { 14 8A 02 00 02 00 02 00 03 00 }
0x6512C: EqIdVal QuestionId: 0x1, Value: 0x1 { 12 06 01 00 01 00 }
0x65132: And { 15 02 }
0x65134: End { 29 02 }
0x65136: SuppressIf { 0A 82 }
0x65138: True { 46 02 }
0x6513A: GrayOutIf { 19 82 }
0x6513C: EqIdVal QuestionId: 0xD, Value: 0x1 { 12 06 0D 00 01 00 }
0x65142: OneOf Prompt: “Boot Mode”, Help: “[UEFI]For any OS that needs pure UEFI.[Legacy Support]For any OS that need legacy support.”, QuestionFlags: 0x4, QuestionId: 0x105E, VarStoreId: 0x1234, VarOffset: 0x79, Flags: 0x10, Size: 8, Min: 0x0, Max: 0x2, Step: 0x0 { 05 91 97 00 98 00 5E 10 34 12 79 00 04 10 00 02 00 }
0x65153: OneOfOption Option: “UEFI” Value: 2, Default { 09 07 9B 00 10 00 02 }
0x6515A: OneOfOption Option: “Legacy Support” Value: 0 { 09 07 99 00 00 00 00 }

and furthermore

0x65183: SuppressIf { 0A 82 }
0x65185: EqIdVal QuestionId: 0x105E, Value: 0x2 { 12 06 5E 10 02 00 }
0x6518B: GrayOutIf { 19 82 }
0x6518D: EqIdValList QuestionId: 0x2, Values: [2, 3] { 14 8A 02 00 02 00 02 00 03 00 }
0x65197: EqIdVal QuestionId: 0x1, Value: 0x1 { 12 06 01 00 01 00 }
0x6519D: And { 15 02 }
0x6519F: End { 29 02 }
0x651A1: OneOf Prompt: “Boot Priority”, Help: “[UEFI First]Try UEFI boot first.[Legacy First]Try legacy boot first.”, QuestionFlags: 0x4, QuestionId: 0x105C, VarStoreId: 0x1234, VarOffset: 0x75, Flags: 0x10, Size: 8, Min: 0x0, Max: 0x1, Step: 0x0 { 05 91 64 00 65 00 5C 10 34 12 75 00 04 10 00 01 00 }
0x651B2: OneOfOption Option: “UEFI First” Value: 0, Default { 09 07 68 00 10 00 00 }
0x651B9: OneOfOption Option: “Legacy First” Value: 1 { 09 07 69 00 00 00 01 }

Trying to set the 0x79 to 0x1 with setup_var_vs results in an error 8 due to write protection.

I can boot with SREP and unlock some other menus, but unfortunately, as Boot is visible as a main form per default, the subforms and options are kept hidden.

I dont have a programmer yet, but I am able to basic navigate in the hex editor and locate the offsets representing the functionality.

Is there any other way to set all the Boot submenus visible without a programmer and if I go the path with editing in the hex editor, is there a need to calculate checksums before flashing? How should this be done?

Thanks for your support!


Edit by Fernando: Thread moved into the “BIOS Problems” Category and title customized

2

@superspeed
Welcome to the Win-Raid Forum!
After having done a Google Search for “Lenovo Legion 15ACH6 BIOS Legacy Boot mode” you will get this KI information:
“The Lenovo Legion 15ACH6 laptop does not support Legacy Boot mode because it is a 2020 model that only uses UEFI (Unified Extensible Firmware Interface) boot mode. You cannot enable Legacy Boot in the BIOS settings for this model, as the option was removed in 2020 on Lenovo products to support modern boot standards.”

This is not true. You can use and boot off SATA drives as well. The only required pre-condition is, that you use the “GUIMode Partition Table” as partition scheme and boot in UEFI mode.

3

Hey Fernando,

thank you for helping out.

May be I have to be a bit more precise on my statement about the drives: the 15ACH6 has no option to attach SATA directly to the mobo in the factory setting, while the 15IMH05 has this option and comes even with one SATA drive from the factory.

HREF

I am aware of the fact that per default there is no Boot suboption for Legacy boot in the BIOS of the 15ACH6H. That is what I am hoping to make visible with some kind of BIOS mod.

Cheers!

4

Just to make it clear: I am not able to solve your problem.
Why do you want to use the Legacy (MBR) partition scheme mode at all? I do not see any advantage for you and your system. You can install Win7 in UEFI mode without any problem.

The only problem with your 15ACH6 laptop is, that it obviously offers only M.2 ports and it is not clear for me, which “Storage Type” (NVMe or SATA) they support. The picture doesn’t make it visible.

5

Trying to boot with USB pendrive created with Rufus (having set GPT + UEFI w/o CSM) leads to the win setup error 0xc000000d, which I mean is the “no drive to install to” error.

I am using an ISO image with integrated NVM drivers and still having no luck. The Storage Type option is neither visible in the factory BIOS nor in the SREP-modified BIOS. The only thing that is related to the drive topic is set already as it should be:

BIOS AHCI

P.S. Just found this old topic:

As I am not aware anymore how the NVMe stuff was integrated, I think, I’ll start slipstreming a new Win7 iso from scratch and see what happens.

6
  1. Which M.2 connected SSD model was your designed target drive?
  2. To which M.2 port was it connected?
  3. Which data transfer protocol does the M.2 port support (look into the manual)?
7

  1. WD SN810 with Lenovo part nr SSS1D33695

  2. Well, in the manual there is no strict enumeration of the slots. On the motherboard there are JSSD0 and JSSD1, so the target NVMe is in the JSSD1

  3. NVMe, PCIe 3.0 x4

I have just created a fresh Win7 setup with NLite with the NVMe updates from MS and NVMe Intel and Samsung drives integrated. Unfortunately on both laptops I am not able to boot in UEFI mode.

Laptop Boot mode Boot priority USB boot Boot media Rufus media type Result
15IMH05 Legacy first Legacy first Enabled USB stick MBR + BIOS 0x000000A5 - BIOS not fully ACPI compliant
UEFI n.a. Enabled USB stick GPT + UEFI Freeze on loading disk.sys
15ACH6 n.a. n.a. enabled USB stick GPT + UEFI 0xc000000d - Boot selection failed because a required device is unaccessible
8

Why did you additionally integrate Intel and Samsung NVMe drivers (you probably don’t mean drives)? The MS Hotfixes should create a matching generic MS NVMe driver and I doubt, that any original Intel or Samsung NVMe driver would work at all with the NVMe Controller of your WD SSD.

Furthermore I recommend to have a deeper look into the chapter “Step 4 - Installation of Win10/11 onto the NVMe SSD”, which you can find within the initial post of >this< thread. The Guide has been written for the installation of Win10/11, but may work with older Windows Operating Systems as well.

1 Like
9

After some busy days I want to give some feedback about this topic…

I dceided to discard any further tries to get the stuff going as I currently dont have the time to dig deeper just due to curiosity. Nevertheless thank you for sharing the useful link from the previous post, which I will definitely get back to more than just once in the future.

P.S. Yes, I meant drivers and not drives

10

Hi @superspeed,

I’ve been following your attempt here. I wanted to share some technical insights regarding the “Legacy/CSM” absence and the hurdles you are facing with Windows 7 on this hardware.

  1. Regarding the BIOS and Legacy Mode
    You are trying to unlock a feature that is likely no longer there. This laptop is essentially a UEFI Class 3 device. The CSM (Compatibility Support Module) isn’t just hidden in the menu; it is almost certainly stripped out of the firmware binary entirely by Lenovo/AMD.
    To re-implement this, one would need to modify the AMD AGESA encapsulation itself. To date, I have never heard of anyone successfully unpacking, customizing, and repacking modern AGESA modules to restore Legacy functionality. It is technically virtually impossible with our current tools.
  2. Regarding your NVMe Driver Issues
    The error 0xc000000d or hanging at disk.sys confirms a driver mismatch.
  • The Problem: You mentioned integrating a mix of Intel, Samsung, and MS Hotfixes. This “cocktail” approach often causes conflicts. Since your laptop likely shipped with a WD or Hynix SSD, the official Samsung/Intel drivers won’t match the Hardware ID, and the generic MS patches might be overridden or conflicted.
  • The Fix: You would strictly need a “Modded Generic NVMe driver” (like the ones modified by Fernando) or a clean integration of only the MS NVMe updates, ensuring they are properly signed.
  1. The Road Ahead (Why it might not be worth it)
    Even if you solve the NVMe driver issue and get past disk.sys, you will immediately hit two more massive walls:
  • VGA/GOP Issue: Since there is no CSM (Int 10h), Win7 will hang on boot/black screen. You would need a UEFI Shim like UefiSeven or FlashBoot Pro to emulate the BIOS interrupts.
  • ACPI BSOD (0x000000A5): The Windows 7 kernel cannot handle the ACPI tables of the Ryzen 5000 platform. You would need a modified acpi.sys just to boot the installer.

Conclusion
Considering that even if you succeed in booting, there are no Windows 7 drivers for your RTX 3070 or the AMD Radeon iGPU (leaving you with a laggy, unaccelerated desktop), the native installation is practically unusable for daily tasks.

I strongly recommend using a Virtual Machine (VMware or Hyper-V) if you need to run specific Win7 software. The native path on this specific machine is a dead end due to the locked-down AGESA and lack of GPU support.

Good luck!

1 Like
11

Hey @Dark_iaji

thank you for this deep dive with the insights. Quite interesting and even if not possible, still very worth-knowing. The shared information shows even more, that the endevour is not worth spending time on it. Your explanation on the facts is very interesting, so thank you very much for sharing!