Tag Archives: ahci

Switching hard drive from IDE mode to AHCI mode (Vista and Windows 7)

Computer Aid Posted on by

Now most PCs now ship with Windows 7 installed on a drive thats in AHCI mode.

Usually because there can be some potential speed benefit.

But occasionally, an ignorant technician will install W7 with the drive set to IDE mode.

I recently needed to take an existing installation of Windows 7, and in an attempt to improve performance, I wanted to change the drive mode from IDE to AHCI.

I know W7 has native support for AHCI, but before jumping across, I decided to do some research first.

It turns out that W7 actually doesn’t automatically switch to AHCI mode once the hard drive has AHCI enabled in the BIOS.

The first step is to actually go into regedit, then look for:

HKLMsystemCurrentControlSetservicesMsahcistart
HKLMsystemCurrentControlSetservicesIastorvstart
Change the start value to: 0 (ie zero)
write down the original value… just in case.
Close regedit, then restart the PC.
While restarting, enter the PC BIOS, and change the HDD setting from IDE to AHCI
W7 will then start using the drive in AHCI mode.

Acer 4920G will not start

Computer Aid Posted on by

Customer says her Acer 4920G laptop will not start.

Sure enough, when the PC boots, Vista complains about missing system files.

A system recovery should fix the problem, but it turns out she didn’t make a Vista recovery disk.

This is a common problem, as most people don’t have the technical knowledge to realise that a recovery disk is important (and good insurance against an expensive repair). I still cannot understand why computer manufacturers cannot supply a system recovery disk… it probably adds an extra $1 to the cost of the PC… yet manufacturers are more than happy to add webcams, fingerprint readers, and other expensive peripherals that many users never use…

Anyway, all she can find is a microsoft office CD.

I take the PC back to the office and take a closer look at the hard drive.

From within the Acer BIOS, there is a section that says the HDD is frozen…

Hmmm not much info out there on what a “frozen” hard drive actually means, but it doesn’t sound good.

I try the SATA drive in another PC, but given that the drive is one of those annoyingly incompatible AHCI drives, I have no choice but to plug it into another Vista PC… but even vista will not detect the drive.

I plug it back into the acer laptop, and then try installing vista from scratch… but no go: vista say “you might not be able to boot from drive”.

Its looking like the drive has failed. I update the BIOS, so that I can run the drive in IDE mode (not AHCI). I then try an XP install, but that also fails (no drive detected).

I try a different HDD, and that works perfectly.

I talk to the customer, and she says she wasn’t happy with Vista anyway, so she is happy pay for an XP licence, a new HDD, and the time for me to install XP, etc.

Luckily, finding XP drivers for this laptop was not as difficult as with some other laptops!

setup did not find any disk drives installed in your computer

Computer Aid Posted on by

Strange things can happen when trying to downgrade from Vista to XP.

In this case, an Asus F7SR laptop needed to be downgraded.

I boot from the XP CD, and it soon tells me:

setup did not find any disk drives installed in your computer

After some searching, I figure its due to BIOS running the hard drive in AHCI mode.

The standard XP CD is not capable of detecting AHCI drives (at least not without making slipstream CDs, or other fancy footwork).

I look in the bios, but there is no way to switch back from AHCI to ATA mode (so that xp installation can detect the hdd).

I do some searching on the net and find the generally suggested solutions are

– switch from AHCI to ATA mode (I cannot)

– slipstream the XP (I don’t really want to do this unless I find myself doing a lot of Vista downgrades)

– Put the XP sata drivers onto a floppy (laptop has no floppy, so a usb floppy drive is an option), and use the SCSI option when the XP CD starts up.

It just happens that I have a USB floppy drive (this is the first time I’ve used it in 3 years!)

But finding the XP AHCI drivers proves difficult.

The Asus website only has vista drivers (and only eSATA drivers).

While at the ASUS website, I see that the latest bios is “203”… the laptop has “202”.

The 203 bios only has a short description: “support both xp and vista”

I download the bios, use the usb floppy to update the bios… its surprising how many BIOSes will still not upgrade via a USB drive!

After the BIOS upgrade, there is now a bios option to operade the hard drive in ATA mode 🙂

After that, the XP installation was typically easy.

Installing XP drivers was more difficult… and thats a story for some another time!