Help for Dell BIOS Modding to enable AVX512

[antercreeper]

1. BootGuard is enabled, which is suck.
2. The module which i am about to crack is SiInitFsp, where is the key function that set the msr register.
   and it is not included in the IBB.
3. After my trial, the machine don’t boot and the PWR LED indicates the SBIOS is corrupted. I think this module may be in the check list and then doesn’t pass.
4. Of course, it is a new machine with warranty, so can’t do PCH replacement.

So i think maybe there are two ways:

1. make some sort of checksum or signature verification to the new module(i am not very clear about that), or just disable it.
2. Re check the function to find if there is any entrance that, maybe something in the NVRAM could control this function. But after my check, maybe it is unavailable. I will send later, and if anyone can do deeper investigation?
3. get a module from other bios or older version(i think it doesn’t have because mine is 1.0.x which is old enough) which has no AVX512 disable function.

Looking forward to any suggestions! I am stuck at it now…

[rofikkernel]

is you using alder lake cpu ?

[antercreeper]

Yes. i5 12500
I check its batch code and the microcode in BIOS(0x15). all is OK.

The only factor is one function in SiInitFsp block the AVX512.

[rofikkernel]

already try hex method gigabyte method

[antercreeper]

The problem now is BootGuard, which is enabled by DELL.
I tried to modify the image, and then bricked. Power Button led blinking shows that the BIOS is corrupted. I thought it is stuck at the second, after the IBB checking, where DELL doing some checksum to verify if the module is valid. So…

[antercreeper]

The first is if there is a way that don’t need to modify that module, if there is any hidden value in NVRAM control this function.
Or the second, make a checksum or signature, or anything else, to make this module valid.
Or the third, disable the checking, disable BG or make it not work(some factory mode?).

[antercreeper]

from IDA:
B9 AF 00 00 00 mov eax 0xAF
0F 32 wrmsr

After search, you can see those two functions, one is AVX and the other is AVX512

[antercreeper]

SiInitFsp.bin.zip (129.5 KB)