Can Anyone Explain ACHI to me?

[msterzer]

I just bought an ABIT IP35 Pro motherboard with the ICH9R chipset and I don't know what to use for my sata drives when setting up the bios. All my drives are SATA including 2 optical drives. It seems I have the choices of SATA as IDE, RAID or, AHCI. I will be using Windows XP Pro. The manual does say that to use RAID with Win xp that I need to make a floppy with the drivers on it before installing Windows. I can't really find the information to make the best use of the mother board. Can anyone advise me?

[athlonxpguy]

Best explanation :

http://en.wikipedia.org/wiki/Advance...ller_Interface

[Peter M]

First of all, it's AHCI not ACHI. Once you figured that, Google is your best friend.

[msterzer]

In my BIOS I have three choices for setting up the SATA drives. 1-SATA as IDE, 2-RAID (not interested in RAID), and 3-AHCI. After reading about AHCI it sounds like the best way to go. My OS drive meets the requirements. Windows will not load if I set the BIOS for SATA to use AHCI. If I set it to SATA as IDE it all loads up real nice like. After reading stuff until I'm going blind is there some trick to it or is it not what its seems.

[Peter M]

Windows needs to be installed with the FINAL storage controller mode. If it was installed with the SATA in legacy IDE mode, then it won't boot after you switch it to AHCI - and vice versa. Make up your mind first, then leave it at that.

XP installation will need a disk with vendor specific AHCI driver for that kind of installation.

[msterzer]

Thanks Peter, I finally found the answer on an ABIT forum. You are correct about needing the drivers on a floppy disk and the f6 button during installation. However it seems that no performance gains have been noticed or tests shown that AHCI is any better than SATA as IDE. Also several folks have been able to switch to AHCI after the OS was installed by updating the drivers on the 2 SATA controllers then shutting down the PC, rebooting and changing the BIOS to AHCI. It's a little more involved than that as registry needs some editing also. Thats a trick I don't care to perform as SATA as IDE is working real well for me. The ABIT manual has no mention of using a floppy to install the drivers for AHCI but does for RAID. I despise the writers of manuals that are not clear as to BIOS settings especially those that need to be done before the OS installation. Not everyone just knows all the little in and outs of BIOS settings, especially with newer boards.

[Peter M]

You are correct in that AHCI doesn't do much toward performance, as long as it's a typical desktop machine. In a server, you'll notice more of a difference from command queuing, hot plug support, and the other bits and pieces that legacy mode doesn't do.

The mid-term benefit of AHCI is that it unifies the programming model for SATA interfaces again, so that vendor specific drivers won't be needed anymore as soon as the operating systems bring generic AHCI support.

[msterzer]

Peter do you see such support happening with Win XP Pro? I figure it won't happen but will with Vista. Just another thing to force one to update to Vista. I personally will stay away from Vista until I absolutely am forced to. Thank you for you time in helping me understand this new hardware/software. I appreciate it.

[Peter M]

It's not like anyone forces you to enable AHCI mode. Backwards compatibility settings are exactly for running older operating systems - and let's face the facts, XP is seven years old.

[msterzer]

How very true.