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It appears that I'm not the only one with such question, but Googling revealed nothing.

For many contemporary ASUS (maybe other manufacturers too?) motherboards there is a setting in BIOS called "ATA/IDE Configuration", which has three options - Disabled, Compatible and Enhanced. If you choose "Enhanced", you also get a choice for "Enhanced mode support on" and then three choices: S-ATA, P-ATA and S-ATA+P-ATA.

I'd like to make sure my SATA drive runs with full AHCI goodness, but which setting do I chose (and on a side note: how can I tell what mode my HDD is running - PATA or SATA)?

(Note: my particular motherboard is P5G41T-M LX with the Intel G41 chipset).

Added: Ok, tried some experiments. Tried all three settings in Enhanced. Whatever I did, didn't affect Windows 7 device manager, although think an additional "ATA Channel" appeared under the SATA+PATA setting (unused though).

Currently in the Device Manager tree there is a node called "IDE ATA/ATAPI controllers" under which there are 6 subnodes:

  • ATA Channel 0
  • ATA Channel 0
  • ATA Channel 1
  • ATA Channel 1
  • Intel(R) 82801G (ICH7 Family) Ultra ATA Storage Controllers - 27DF
  • Intel(R) 82081GB/GR/GH (ICH7 Familiy) Serial ATA Storage Controller - 27C0

Yes, that's right, there are two of "ATA Channel 0" and "ATA Channel 1". Also, under the first one of "ATA Channel 0" it is written that it supports 2 devices and it lists my DVD-ROM as UDMA4. Under the second "ATA Channel 0" lives my HDD in UDMA5. Note that BIOS also detected the drive as UDMA5. The drive itself is a Samsung HD403LJ.

I also tried the Windows 7 enable AHCI hack with the mode set to Enhanced/SATA in BIOS. Still no effect.

Perhaps my drive already is in AHCI mode and I just don't know it?

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up vote 5 down vote accepted

You can tell by looking in your OS' device list. If the device is attached to an IDE channel, it's not running in AHCI mode.

Enhanced/SATA allows you to map SATA devices to IDE, so operating systems without AHCI support can still make use of the disks. SATA+PATA usually means that SATA is mapped to primary IDE, while PATA is mapped to secondary IDE (in different possible combinations, eg. physical primary master/slave to logical secondary master/slave, or physical primary/secondary master to logical secondary master/slave).

  • Choose Enhanced mode / PATA if you have an IDE device you'd like to support
  • Choose Compatible mode if you have an IDE device and enhanced mode doesn't work with your OS
  • Choose Enhanced mode with SATA if you have SATA devices that your OS can't find (plain SATA if you have no IDE devices attached, SATA+PATA if you have SATA and IDE)
  • Choose Disabled if you have no IDE devices and SATA devices work properly in AHCI mode

It's also possible that the chipset on your board does not support AHCI, Intel is somewhat sadistic about that (they even have different revisions of the same chip, with the same name, with AHCI enabled and disabled!). And even if the chipset supports AHCI, the BIOS can disable it!

In either case, the SATA ports will always be provided with an "IDE" interface, and this configuration option above is only relevant in rare cornercases (very old operating system that supports only 4 IDE devices in total), where you have to "stuff together" IDE and SATA to let the OS access all devices through 2 IDE controllers ("primary" and "secondary").

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I have never seen a board that did it this way (which is why I answered basically the exact opposite). Which vendor's BIOS lists it this way? – Shinrai May 3 '11 at 14:13
My OS is Windows 7. I've tried several options, but my SATA HDD stays under the same "ATA Channel 0" as my PATA DVD-RW drive. It's also listed in UDMA5 mode. I understand that I need the "Enhanced/PATA" mode then, to have my HDD as AHCI and CD-ROM as PATA? Kinda tried this now, but still no effect. – Vilx- May 3 '11 at 14:23
Intel hardware documentation. Of course, BIOS could mean different things with these terms, but on the (non-intel) systems I've seen a BIOS, "IDE/ATA Configuration" was separate from SATA configuration, and was really concerned about what appears on the ATA/IDE ports. So configuring IDE/ATA to support SATA means that SATA as its own entity (ie. AHCI) was disabled, and provided SATA via the legacy/compatibility IDE interfaces. – Patrick Georgi May 3 '11 at 14:24
@Patrick - You might be right on this one, since it seems laid out a bit oddly, but that's not an across-the-board standard for sure. I've seen motherboards where the options are explicitly 'Compatibility' and 'AHCI', haha. I guess @Vilx should try disabling this and see if that gets his hard drive working in AHCI mode... – Shinrai May 3 '11 at 14:29
The disk supports it, but the controller doesn't support the protocol necessary for that. It may be the southbridge (some ICH models support AHCI, some don't, and the model name doesn't state it), it may be the BIOS that disables AHCI even though it would work on that hardware. A tool (like AIDA) that queries the disk about its capabilities gets told what the disk can do theoretically, not what it can do on this controller. – Patrick Georgi May 3 '11 at 15:02

I have the same chipset ICH7 - G41 on a Dell Inspiron One 19. This 2009 machine has the IDE/ATA 82801gb/gr/gh SATA controller. Note that 82801GB does not support AHCI. Intel ICH7 wikipedia

To answer your question - ATA/IDE is set so that Windows will BOOT.

(Including booting to Windows XP Vista 7 8.1 and 10 installers.)

In my case, with a replacement WD hard drive just installed, Compatible allows Windows disks to load.
Disabled = NO hard drive found, prompts and beeps.
Enhanced leads to Windows 10 installer crash "MACHINE CHECK EXCEPTION". The choice is easy.

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