✧✦Catherine✦✧Feb 27

heyyyyyy. check this out

i bought one of those chinese motherboards which get the UEFI package from American Megatrends and then enable options with the guiding principle of "YES."

check out how many juicy bits it has

you can turn the memory scrambler on and off! it even tells you the seed it has on, i think, this specific boot?

Show thread✧✦Catherine✦✧Feb 27

it has soooo many PCIe configuration options. port bifurcation is just the start of it. there's probably an option for every power related register

you can enable "PCIe Stop & Scream", whatever the hell that is

Show thread✧✦Catherine✦✧Feb 27
you can disable GPIO lockdown!
there's a function that prevents malicious UEFI Flash wearout, a type of attack I have not considered before. also you can turn it off
you can set UEFI boot stage breakpoints!
Show thread✧✦Catherine✦✧Feb 27

I think my favorite one is just

PCIe Stop & Scream Support [Disable]

Show thread✧✦Catherine✦✧Feb 27

when you open the IntelRCSetup (what's RC?) the setup utility tells you "if you change some of these settings the system may malfunction"

that's an understatement of the year

Show thread✧✦Catherine✦✧Feb 27
it also lets you unlock these specific MSRs that are completely undocumented and have no search hits besides some hackintosh person poking at them. no idea what they do or why there's a toggle
Show threadPeter Bosch
@whitequark 0x3A is just IA32_FEATURE_CONTROL which allows enabling things like VMX and SGX
Feb 27 at 9:26pmWeb
Show threadiximeowFeb 27

@peterbjornx @whitequark and E2h relates to c-state control ( the useful reference for intel is https://www.intel.com/content/dam/develop/external/us/en/documents/335592-sdm-vol-4.pdf)

i dunno what "CSR" means in this context though?

Show thread✧✦Catherine✦✧Feb 27
@iximeow @peterbjornx Configuration/Status Register maybe? not sure though
Show threadiximeowFeb 27
@whitequark @peterbjornx could be? in which case i figure it's something in the PCH or something but nothing obvious lined up