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Curious: Switching to IDE mode after AHCI setup

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Hi everyone,

Sorry if this is kind of off-topic, but I know I'll get an intelligent response here.

My system is P8P67. I've got hard drives on all the internal SATA ports (Intel ICH6 and Marvell 1923), all running in AHCI mode, formatted and operating nicely, both in Windows 7 and Lion.

Now, I need to use a certain piece of software which will be accessing a SATA DVD drive which will be attached to one of the ICH6 headers, and here's the kicker... this software requires IDE mode to access the drive correctly.

What will happen if I switch SATA from AHCI to IDE mode in BIOS? Will I still be able to boot from my Win 7 drive, even though its entire life has been an AHCI one? Will I have difficulty booting back into either of my boot volumes if I then go back into BIOS and switch back to AHCI mode?

I guess I'm unclear if these two modes are incompatible with the same disk format between the two of them; can you create and format and use a disk under AHCI, and then just switch to IDE and have everything function (without SMART, NCQ, etc.) okay still?
 
Mac OS won't boot anymore, unless you use 2 differents SATA chip (eg integrated and a marvell added by the manufacturer, wich are 2 differents settings you can set in the bios), but no problem for windows 7 (but you'll have to edit a key in the registry to go back to AHCI)
 
So then, I could theoretically unplug all drives except for my Windows boot drive, set that chipset to IDE, boot up Win 7, do what I have to do, set whatever key in the registry I have to, shutdown, reconnect my drives, reboot back in AHCI, and everything should still be bootable and readable?

FWIW, can you give me a nudge in the right direction to find more about what key needs to be edited in the registry?
 
Correct.
You habe to change
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci

To 0.

I din't think the rest is needed (do this before the reboot to AHCI mode ;) )
 
Flym4n said:
I din't think the rest is needed (do this before the reboot to AHCI mode ;) )

Thanks for your patience—just to clarify... I don't need to disconnect my other Mac/Boot drives from the chipset, even if it is going to be set to IDE? i.e., I'll still be able to boot from them into Lion after setting back to AHCI, if they've been accessed via IDE through Windows 7?

Or do you mean I don't need to set the other keys?

Kind of ironic that I didn't have this problem on my old Mac Pro, as by necessity I had Win XP installed in emulated IDE mode through Boot Camp on that system. When I sold it and built my Hack, though, I tried installing XP and kept getting BSOD (I assume now, because I was set to AHCI mode, and it didn't have AHCI drivers built in, right?)
 
Both actually :)
Only one key in windows to hack, and you don't need to remove the othe drives ;)
 
Just out of curiosity... (and your continued help is truly appreciated) why is regedit needed only when going back to AHCI, and not before setting to IDE?
 
I don't know, it's set automagically.
Maybe a way to improve compability with old IDE hardware?
 
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