Hi, i'm Italian, sorry for my english.
I have a 27" iMac 10,1 late 2009. I have installed a samsung 840 evo 250 GB instead superdrive.
I have 1TB mac original 7200 rpm hard drive and the sad instead superdrive. I have 2 partitions in SSD one with mavericks and the other with windows 8.1.
Can i enable AHCI mode? What is the correct procedure? Exist a program? Thanks. I HAVE TRY MANY DRIVER BUT HDD REMAIN IN IDE MODE...

i have an ibook 5.1 . he have the same controller, and i have the same problem....

The Windows version of NVIDIA MCP (Media & Communications Processor) chipsets differ from the iMac version in that they have a BIOS with a RAID Option ROM that enables AHCI mode by changing the Device ID (and also PCI registers) and later installing Nvidia's proprietary AHCI/RAID driver in Windows.

As the 27" 2009 iMac uses EFI and allows Windows to boot through BIOS emulation, you are limited by whatever Apple provides in Boot Camp, which is IDE Mode by default

If you read this, you can see that others have faced the same problem with the Nvidia chipset trying to enable AHCI in Linux as well as Windows.

You can get Linux to recognise the SATA controller as AHCI capable by adding the correct PCI register info to the GRUB bootloader configuration (grub.cfg) e.g.

Zitat

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| # setpci -d 10de:0ab5 9c.b=06

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I take it you have read here, where others have installed Windows Vista/Windows 7/Windows 8 in UEFI mode on a GPT partitioned hard drive (without Mac OS installed on the drive at all) which automatically enables AHCI mode - I noticed you posted there also.

Someone could *possibly* solve the problem by investigating the differences in the values of the PCI registers for the device ID 10de:0ab5 when Windows has been installed using UEFI (AHCI mode) and comparing it with a Windows installation using Bootcamp (IDE mode) - but to do this they must have access to a 27" 2009 iMac with the latest firmware installed.

[Edit] Reading through this Apple support thread on this issue, it seems that even force installing an AHCI driver through Windows device manager will not correctly enable AHCI.