Snow Leopard DSDT for the Gigabyte H55M-UD2H

Installing Snow Leopard on the H55M-UD2H is relatively easy. I’m using an i3, but due to the lack of full support (no Apple Macs use it at present), I’d suggest going with the i5 which has recently gained some support.

I have provided a DSDT which I finished most of – it has all the basic fixes, and adds USB support properly so that 10.6.3 doesn’t choke – the only thing left to add is the sound (which you’ll probably want), and switch the IDE setting to SATA in the DSDT (which you probably won’t care about).

WARNING: USE AT YOUR OWN RISK! No guarantees. It worked for me, but for all I know it might melt down your system!

You can grab it here:
GA-H55M-UD2H – DSDT for F8 BIOS (

Unzip it first. Generally, you put the DSDT.aml in your /Extra folder, but it could depend based on your bootloader.

I did the following:
-Minor fixes so it would compile
-CMOS reset fix (so it won’t clear your CMOS every time you shutdown/restart)
-TMR, HPET, PIC fixes
-SBUS fix (for sleep although with the onboard video I couldn’t get it to sleep anyway)
-USB -> UHCI/EHCI fix (so your USB should work properly and won’t break at 10.6.3)

I would strongly recommend using iBoot Supported + MultiBeast. Tony’s also got fantastic tutorials on his site for installing, and others that can help you if you decide to try further editing the DSDT for audio (though I believe you’ll still need a kext) and for IDE -> SATA. His tutorials helped me a lot – I was learning from scratch and can now do DSDT edits! In addition, there’s a bit on putting your CPU and video card stuff on his site also, so check it out and support his work!

I’ll note the following about this motherboard, DSDT, and other bits:
-I strongly recommend using the F8 bios, because that’s what this DSDT was based on. Others may work, but they may not.
-You should be able to remove most kexts from /Extra/Extensions. You will still need fakesmc.kext, but the rest might be able to go. Remove them one at a time though so you know which one is causing the problem if something breaks.
-If you mess something up (remove certain kexts without having DSDT.aml in place for instance), your CMOS might get screwy. One of the symptoms is that the physical reset button stops working! To fix this, unplug the computer and remove the CMOS/BIOS battery for a few hours, as well as shorting the cmos reset pins for a second or two. When you put the battery back in you’ll have to set all your BIOS settings again, but the reset button should work correctly.
-Assuming you use the mach_kernel from TonyMac’s iBoot Supported (and copy it to your root) – something that may be necessary to support your i3/i5, you will notice that removing the NullCPUPowerManagement kext makes AppleIntelCPUPowerManagement die during boot (so it won’t boot) even though you have the DSDT! This happens because the kernel version is different from the AppleIntelCPU…..kext. To fix this you must download the MacBookProUpdate1.3 and use Pacifist to install the 2 AppleIntelCPUPowerManagement kexts. Don’t delete NullCPUPowerManagement until you’ve pulled/installed those kexts or you’ll end up having to boot from the CD.
-It is currently impossible to get the onboard Intel HD Graphics to work with QE/CI. It will not load any kexts. Even the ones from the MacBookProUpdate linked above will not work (the FrameBuffer one will stop you from booting and the others wont be detected even if you add your deviceID). I am certain this is what’s keeping this motherboard from sleeping. Use an external video card (preferably a well-supported nVidia) and I’ll bet sleep will work (confirmed – sleep is fine with an external video card).
-On the i3, speedstep will only work if you add a certain entry to smbios.plist. “About this Mac” will however show you as an i5. There may be a different entry that will detect the i3, but I have not found it if it exists. The i5 one that appears to work is the following entry in smbios.plist:

-I recommend using the MacBookPro5,1 from MultiBeast. Trying to change it to 6,1 or using another one tends to stop SpeedStep from working if you do the above (if you don’t care about speedstep, by all means, go nuts).
-Adding your CPU to the DSDT is probably the best option if you’re intent on speedstep, but it’s dangerous if you don’t know what you’re doing, and can be quite complicated. In the event you’re using an i3 540, you can try my CPU modded one for this motherboard but it’s risky – even if you’re using the i3 540, something could be different. It’s always possible that I’ve made a mistake in it too. It’s available by clicking here (use at your own risk – you’ve been warned!): GA-H55M-UD2H DSDT with i3 540 PSS entries. WARNING!!!! This can seriously mess up (damage) your motherboard, CPU, or something else if something isn’t correct. Never under any circumstance even try it on another CPU.