Modified UEFI Rom FAQ
These are some of the most frequently asked questions I see in relation to modified/patched bioses.
Which brands need a modified bios?
Asus, Asrock, MSI, Foxconn, Zotac and Biostar.
Essentially any board which uses UEFI, apart from Gigabyte.
brycv has found that there isn't a way to flash a modified bios on Intel boards.
Pre-1155 boards (1156, 1366 etc) do not require these.
LGA2011 boards of the above brands will eventually require modified roms, however LGA2011 cannot use native power management right now.
Is it hard to flash a modified/patched bios?
The bioses have already been modified for you, therefore all you do is update your bios as you would with a regular bios. Consult your boards manual for more info.
Asus Z77 users must use the USB Flashback feature on their boards. This is because the .cap roms are checked for modification when using the other bios update procedures (DOS update, ezflash2, updating through Windows)
Why is a modified bios needed?
There is a part of the UEFI bioses which deals with cstate config. All mobo makers since last year (except any who were using Award bios, and Gigabyte uefi) have left this part locked. When the appleintelcpupowermanagement (aicpupm for short) kext tries to write to this part, it cannot and kernel panics.
Gigabyte UEFI boards do not engage this lock from the factory. For other brand boards using UEFI, it must be done ourselves. Hopefully the other mobo makers take Gigabyte's lead and remove this lock.
What is modified?
The bios is modified to remove the lock. This means we no longer have an issue, and can boot with the native power management kext without problem.
Will Windows installations be affected?
The modification does not make a difference to other OS.
I have already used nullcpu, or easybeast etc, but want to used a modfied rom instead. What do I have to do?
You want to return to a stock state if possible. If you don't, it'll be pointless flashing a modded rom as you won't see the benefit.
If you installed nullcpu (or used easybeast), delete it and repair permissions.
On the subject of easybeast, as you have a UEFI board, it is highly unlikely you need the kexts which easybeast installs. Find out what they are, and delete them.
After flashing the modded rom, your bios settings will most likely be returned to default. Make sure to set things like AHCI, and boot order before attempting to boot into OSX.
Does flashing a modified bios mean that i won't need to use a patched/modified DSDT?
The modification to the bios does not alter the native DSDT.
Whether your board needs a modified DSDT or not is unrelated to the modified bios.
Most UEFI boards do not need a modified DSDT, and those that do only require a slight alteration in most cases.
Using HDMI audio requires the use of hdef edits to the DSDT (following toleda's guides).
Does flashing a modified bios void my warranty?
Depends who you ask, and what the situation is.
The modified bios is essentially almost identical to a stock bios; the modification is minuscule in terms of what is changed, and it is not visually noticeable. No features are added or removed.
If a stock bios is flashed over a modified bios, the bios is now returned to stock. No remnants of 'modification' will remain.
If you cannot flash a stock bios, such as situations where your board dies, then on some boards (eg. Asus) you can replace the bios chip if needed.
My personal view is whether anyone will actually check if push came to shove. Possible that if it is RTM they may check, but a store return/replacement is highly unlikely to check.
There has been no reports that i am aware of where an RMA was turned down to the presence of a modded rom, however there is still a risk if you send it back to a store/manufacturer with the modified bios, and this ultimately something to consider.
Is there an alternative to the modified bioses?
Yes; a patched appleintelcpupowermanagement.kext, or nullcpupowermanagement.kext
However, these alternatives have their downsides.
the patched aicpupm kext has to be reinstalled after most OSX updates. Also, if the aicpupm is updated by Apple, the new aicpupm kext must be patched, and this is not always immediately done or available.
nullcpu overrides native power management, therefore sleep and speedstep will not work.
Using a modified bios is the cleanest way, as it requires no alterations or additional kexts to OSX.
Can i modify the rom myself, and if so what are the patched bios threads used for?
Yes, you can do it yourself.
The methods to unlock the older and newer style of UEFI bioses were found by RevoGirl, however since her passing, her blog was taken down.
The process of modifying the rom can seem quite daunting, so in order to simply the process for users, and give as many people as possible the chance of using native power management, the patched bios threads were started.
dgsga has made a guide on modifying the later style of uefi bioses. google "Unlocking the new Asus 3xxx Sandy/Ivy Bridge bios" for more info.