Right now I have everything working on the following hardware with OS X 10.6.5:

P6X58D-E
i7 920 D0
6GB Corsair RAM
ATI 5850

However, I can't boot into the 64-bit kernel if I have SleepEnabler.kext installed along with NullCPUPowerManagement.kext. I will list the combinations I've tried.

NullCPUPowerManagement.kext: 64-bit and 32-bit both work.
SleepEnabler.kext: 64-bit and 32-bit both work.
NullCPUPowerManagement + SleepEnabler.kext: Only 32-bit works.

So I now have to choose between performance (my 920 is overclocked) and sleep if I want 64-bit, or I can have both with 32-bit.

Does anyone have an idea as to how I may go about solving the problem?

Thanks in advance for any help.

With the P6X58D-E, you ought to be able to run without NullCPUPM or SleepEnabler if you did your DSDT right. I believe that's one of the ASUS boards that works. Should be a guide around somewhere like insanelymac.com. Then you can 64 bit and you don't even need those kexts anymore.

I'm currently using the DSDT.aml file from the P6X58D Premium guide, but I still need the kexts for audio and sleep. NullCPUPowerManagement is not necessary if my CPU is running at stock speeds, but I would like to overclock it. I'll try searching for a more specific DSDT.aml.

Thanks for the help!

If native CPU Powermanagment works by correct P- & C-Stats in DSDT, there is no need for SleepEnabler.kext as AppleIntelCPUPowermanagment does the job.

What do you promise yourself from running your OCed CPU at full power, when your system is in idle mode?^^

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When my CPU is overclocked to just 3.61 Ghz with HT, I see a significant performance benefit of disabling native power management. In Geekbench my score without NullCPUPowerManagement is around 8,000 which is pretty much the same as when the CPU is not overclocked, but I can reach scores of over 10,000 if I enable it, thus disabling AppleIntelCPUPowerManagement.kext.

Despite this, I think I've decided that I won't actually see much advantage in overclocking the already blazing fast Core i7, but I was really hoping I could run at around 4 Ghz with HT, as I do in Windows. Really, I don't even use that much processing power, so it's more of the fact that I CAN do it rather than it bringing any tangible performance boost.

Thanks for the help

One guy told me that if you take SleepEnabler out of /E/E, and then wait until after you boot and log in to load it manually, it will provide sleep functionality without causing a panic, and you can do 64 bit and NullCPUPM. I haven't tried it because it seems like too much of a PITA.