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AHCI drive

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December 11, 2009 8:58:08 PM

What is an AHCI drive. I have a new motherboard (ASUS M378-VM) that has five SATA ports - SATA 1 (Red in connector) SATA 2 (Red) SATA 3 (RED) SATA 4 (Black) and SATA 5 (Black). The store manager told me that it would control five SATA hard drives, however, the manual has a notation that states, "Due to Chipset limitations, SATA 4 and SATA 5 do not support IDE mode, only support AHCI and RAID mode". While the store manager insists that this board will support five SATA IDE drives, I would like some clarification, please and what is AHCI? Thanks, Jim

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a b G Storage
December 13, 2009 1:42:45 PM

You want AHCI, its faster and better than IDE (i don't know how to explain but think of them as connection types) AHCI is faster so don't worry about it not supporting IDE.
December 13, 2009 6:47:55 PM

Thanks, Blackhawk192, then I have two questions: My oldest SATA drive is about four years old and my newest is about a year old. Can I institute AHIC on any SATA drive? The second question is will I lose data if I do implement AHIC on these drives, that are nearly full?

Thanks, again,

Jim
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a b G Storage
December 13, 2009 9:39:00 PM

Not sure about that, storage configs and all of that isn't my stronghold as i am still learning many things myself and asking questions so somebody more expirienced will probably give a better answer.
December 13, 2009 11:05:45 PM

Thanks, anyway, I'm in the same kind of boat you're in, just a ways behind you. It seems that every time I begin to become comfortable with current technology, they change things and I'm obsolete. again.

Jim
a c 415 G Storage
December 14, 2009 4:26:30 PM

Jim_12 said:
What is an AHCI drive ... what is AHCI? Thanks, Jim
There's no such thing as an "AHCI drive" - what you're talking about is a SATA drive. AHCI (Advanced Host Communication Interface) is the software API (application programming interface) that lets a Windows device driver talk to a SATA drive.

So the deal is: you buy a SATA drive, plug it into a SATA port on your motherboard, and when you install Windows it chooses an AHCI driver to talk to the disks.

Windows XP doesn't include AHCI drivers, so you have to manually load them when you install Windows. An alternative is that some motherboards have an "IDE Mode" that you can configure to fool Windows XP into thinking it's talking to an IDE drive using the older ATAPI drivers. But if you're using Vista or Windows 7, there's no need to do that.
a c 328 G Storage
December 15, 2009 8:03:03 PM

I am NOT sure about this, but it is my understanding that, if a SATA drive has been used (data on it already, etc) in native SATA mode, you cannot access it in AHCI mode. However, for the near term that is not a problem for you - the shop people didn't tell you the whole story.

Your mobo has 5 SATA ports, yes, but they are supplied / managed by two different controller chips. ALL of the ports should operate just fine as SATA ports. And it happens that one of the controllers can do IDE Emulation, and one cannot.

Any SATA drive can be connected to any SATA port. Then the port needs to be configured in the BIOS Setup screens, and there may be up to four possible modes. Basic "native SATA" - the port just handles it as a SATA drive. AHCI is a slightly more advanced port / drive interface protocol that gives you some extra features, some of which do not matter to many home users. RAID allows you to use the drive in a RAID array via a software RAID management system built into the mobo BIOS. Now, up to and including all versions of Windows XP, the OS had its own built-in drivers for using IDE devices and ATAPI, but NOT for these newer systems of SATA, AHCI or RAID. However, Windows Install utility did already have a way to deal with non-IDE devices for purposes of installing and running Windows - a step early in the Install routine that allowed you to load in external drivers you need for non-IDE units like SCSI, etc. So this method was available to set up a system with SATA, AHCI or RAID drives. BUT it only knew how to load those drives from a FLOPPY disk! And many newer systems did not have one.

The great solution offered by mobo makers and their BIOS writers was a fourth "mode" on the SATA port configuration menu: IDE (or PATA) Emulation. If you choose this, the mobo intervenes a bit and makes a real SATA drive appear to Windows to be a plain old IDE drive, and Windows is blissfully happy and ignorant of the deception. The downside is that making this choice means you do not get to use the extra features of true SATA or AHCI. NOTE that this still did not remove the necessity to load RAID drivers if you planned that, but that is was your problem to handle. And, if you actually wanted to use native SATA or AHCI modes, you still had to find a way to provide the drivers on a floppy during the Windows XP Install.

Next came Vista and then Win 7. They both added built-in drivers for SATA and AHCI modes (but not RAID), making the special IDE Emulation mode unnecessary. The also allowed loading external drivers from USB flash drives or optical disks, removing the need for a floppy drive even if you were going to install them to a RAID array to boot from.

So, in your case with older SATA drives containing data, the simplest solution will be to connect them to one of the first three SATA ports that DO have the ability to supply the IDE Emulation mode. Now, whether you need that mode, or whether you can simply use them as native SATA devices, depends on which Windows you have already installed, and how. If it was Win XP with no extra drivers installed originally, you will need the IDE Emulation mode to access those disks. If you have Vista or Win 7 installed, that probably can deal with your real SATA units in pure native SATA mode.

Now, when it comes time to use SATA ports 4 and 5, you will not be able to use IDE Emulation mode. I'm actually a little puzzled that the manual does not say they support plain basic SATA mode, but maybe they do. If you have Vista or Win 7 as your OS, they have the SATA and AHCI drivers and will be able to handle any SATA drive on those ports. If you have Win XP, you will have to install the SATA or AHCI driver in it to be able to use those ports - not a big problem, done within Windows just like any other driver installation. You will NOT be able to use those ports for a BOOT drive with Win XP because they cannot be made to look like old IDE drives, but that won't be a real issue for you.
a c 415 G Storage
December 15, 2009 10:12:58 PM

Paperdoc said:
I am NOT sure about this, but it is my understanding that, if a SATA drive has been used (data on it already, etc) in native SATA mode, you cannot access it in AHCI mode.


"Native SATA mode" and "AHCI mode" are the same thing. I think you're referring to "IDE Emulation mode" versus "AHCI mode".

It's not really about whether the drive has been "used" or not, it's about which disk drivers the operating system is using. If you install Windows with the drive in one mode, it will fail to boot if you switch it into a different mode because the driver's it's using aren't compatible with the new mode. This sticky post at the top of the Storage Forum describes how to get around this problem.
December 16, 2009 3:34:09 AM

Thanks, Paperdoc. I had sent an inquiry to Asus prior to posting the question on this website and, in desperation, I called Asus yesterday morning. The tech I talked to said I could not use the last two SATA ports (SATA 4 and SATA 5), as independent SATA drives. With that determination, I returned the board to the store for a refund. This morning, I received a reply to my inquiry to Asus, saying that I could use those last two ports to drive any SATA drive, and wanted to know the manual and page number that I read that I could only use these ports for RAID or AHCI.

After returning the Asus board, I procured another mainboard from another local store. It's a Gigabyte GA-P55-UD4P. I hope I can get this one up and running but I'm having trouble with it. It's seeing the CD and the hard drive but I can't boot from the CD. I have the CD set as first boot device and the screen says "booting from CD (Windows Xp is loaded, but, after a short pause, it proceeds loading the old OS on the C drive. Once the OS is loaded, neither the pointing device nor the keyboard work. I know the drivers are all wrong, but I have to find out why it won't start with the CD - object being a clean install.

Jim
a c 328 G Storage
December 16, 2009 12:41:07 PM

If you want to do a clean install, your first step is to use the Win XP Install CD to boot from and tell it to Delete all the Partitions it finds on the HDD you plan to install to. However, I see that your machine won't complete its boot from the CD.

I suggest you check the BIOS Setup screen where Boot Priority is set. Temporarily set to it use ONLY the optical drive and not even try the HDD. Maybe under those settings you can manage to boot into the Install routines. From there, Delete all the Partitions on the HDD and once that is complete, stop the process and reboot. Go immediately into BIOS setup again and set the HDD (now "empty") as the second boot device choice, Save and Exit, and this time it ought to boot cleanly from the optical drive (since there's nothing on the HDD) and get you going for the clean Install.
a c 328 G Storage
December 16, 2009 12:59:44 PM

sminlal said:
"Native SATA mode" and "AHCI mode" are the same thing. I think you're referring to "IDE Emulation mode" versus "AHCI mode".

It's not really about whether the drive has been "used" or not, it's about which disk drivers the operating system is using. If you install Windows with the drive in one mode, it will fail to boot if you switch it into a different mode because the driver's it's using aren't compatible with the new mode. This sticky post at the top of the Storage Forum describes how to get around this problem.


Sminlal, thanks for the note about this - it got me looking for more info. I am familiar with so many mobo BIOS's that offer "SATA" or "Native SATA" modes distinct from "IDE Emulation" and "AHCI" that I believed they were all different. Prompted by your note, my reading now suggests that AHCI drivers are necessary to actually use all of the new features made available by the SATA hardware interface, but early implementers often avoided doing that (in very early cases, by necessity because the AHCI API had not yet been defined). Some provided a so-called "SATA" driver that really just implemented the older IDE system, and in effect provided just an IDE Emulation under a SATA driver name. Others uses their proprietary driver designs to implement some but not all of the new SATA capabilities in a "non-standard" way. But the correct way to use all of SATA's features is now via an AHCI driver.

By the way, what I meant by using the term, "used" drive, is a drive that has data on it that you want access to. I'm still not clear whether a non-bootable drive containing data written under an IDE Emulation mode could be accessed properly if its SATA port mode were changed to AHCI and the appropriate driver installed in Windows. But I certainly understand that Win XP installed without an AHCI driver "added in" could not access and boot from a drive whose mode was changed from IDE Emulation to AHCI. Come to think of it, I suspect even Vista or Win 7, both of which have AHCI drivers "built in", might have a problem booting from a drive whose mode had been changed. This is all assuming you did no other adjustments, whereas your reference to the sticky shows you how to do those.
a c 415 G Storage
December 16, 2009 3:55:38 PM

Paperdoc said:
I'm still not clear whether a non-bootable drive containing data written under an IDE Emulation mode could be accessed properly if its SATA port mode were changed to AHCI and the appropriate driver installed in Windows.
If the OS can boot, then it will be able to load the appropriate driver and you'll be able to access the drive. The "mode" of the drive has nothing to do with the data actually stored on the drive, so there's absolutely no reason why you wouldn't be able to use the drive as long as you've got the correct driver.

This isn't true of RAID, of course, because with with most RAID organizations the data on the drive actually is different.
a c 328 G Storage
December 16, 2009 5:54:36 PM

Yeah, RAID is a different and non-standardized group of animals, unlike AHCI or good old IDE. Actually, I recognize that the data organization on the unit is no different. I simply did not know whether Windows would object to trying to access a HDD using the AHCI drivers (mandated by having the SATA port mode set to AHCI), if it also had conflicting information from the drive itself (MBR, Partition table, or Root Directory data?) that it originally was written in a non-AHCI mode. If it works, it works!
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