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Questions about AHCI Mode (GA-EX58-UD4P motherboard)

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March 14, 2010 9:17:04 PM

Hello all. Thanks to posts I read in these forums, I was recently able to enable AHCI mode in both XP & Windows 7 on my dual-boot machine after having already installed windows.

Now that I'm running with AHCI active in the BIOS, I have a couple of questions concerning some strange things I've noticed.

First, any device I plug into a SATA port will now (like it should) be automatically recognized by Windows without having to reboot. But I'm confused as to why I never have an option to safely remove the hardware if I want to eject the device. I know other people (using different MBs?) have the option to remove the hardware in their taskbar. Is this a condition of my BIOS? (It's using version F7 btw.) And is it safe to just unplug the devices like I would a USB flash drive?

Second, when AHCI mode is enabled, my BIOS cannot identify any device plugged into a SATA port. So if I go into Standard CMOS Features and look at the different IDE channels, they all show as "None." If I disable AHCI mode and reboot, all connected devices then show under the correct IDE channel. This kind of annoys me, since the BIOS is an easy way to see if you are experiencing a hardware problem of some sort should a device not be recognized in windows. Again, is this an issue with the BIOS, and is there any way to configure it so it shows all devices while in AHCI mode?

Thanks!
a c 177 V Motherboard
March 14, 2010 9:24:47 PM

The 'remove' option is to make sure the in-memory disk cache is 'flushed' to the disk, before the connection is physically 'broken'...

The AHCI-configured disks are handled by a different 'chunk' of the BIOS (usually, an 'option ROM' addition) rather than the IDE compatibility 'normal' mechanism; if you disable AHCI, they should 're-appear' on the IDE list, and it shouldn't 'damage' the disk; I often do exactly that to by-pass the slow 'discovery' by my RAID BIOS when I need to reboot a bunch of times in a row - I just 'insert' a bootable CD to 'intercept' the boot, and make sure I don't 'hit the disk' during an 'unRAIDed' boot, ruining the RAID arrays...
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a c 295 V Motherboard
March 15, 2010 12:46:37 AM

1- The AHCI mode is for unplug your drives like a USB flash drive.
2- You can't see your drives in AHCI mode, because both OS (XP and 7) was installed on IDE mode, if you want see your drives in AHCI mode, you need install the OS in that mode.
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a c 177 V Motherboard
March 15, 2010 3:27:43 AM

If your boot disk is AHCI, Xp needs a 'pre-install' (<F6>) driver to be able to 'see' it; switching back & forth is not an easy option (but often possible, with a bit of work); seven has AHCI drivers 'native', and doesn't really care... For other (non-boot) drives, neither OS is bothered; I boot four 'flavors' of seven, vista 64, Xp 32, and Debian linux 32 & 64 - none of 'em give a rip either way (but I always install all the drivers - first thing!)...
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March 15, 2010 12:33:47 PM

Just to clarify, I can see all my drives just fine in Windows. The BIOS is where I don't see any of the drives listed. (I have to toggle off AHCI mode and reboot into the BIOS, then the different IDE channels on the "Standard CMOS Features" screen will show the various devices.) So I'm fairly certain this is not a windows install or driver issue, but instead there's something quirky about how the BIOS identifies SATA devices.

Not sure if a BIOS update will correct this (I'm using version F7 but I rather not flash unless I'm sure a newer BIOS will work), or if there is a configuration option in the BIOS that I have to find to fix this.
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a c 295 V Motherboard
March 15, 2010 12:43:20 PM

Ok, Can you see your drives when you boot in IDE mode right?, because your say that you can't boot in AHCI mode.
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a c 177 V Motherboard
March 15, 2010 1:51:57 PM

Here's how it works:

When it starts POST, the BIOS does a chunk of code called 'discovery'; in this code, it sort of 'wiggles its fingers', and counts how many there are... It sees how much RAM it has, and how it's organized (the screen says 'testing', but it's not really - it's just 'ennumerating'!); if it has anything on any of its PCI or PCIe busses, and how they're hooked up; whether it has any drives, and how many, and what type and organization...

If AHCI and RAID are disabled, the drive discovery is done early, in IDE mode (for compatibilty, even if they're SATA drives), and even though there is no 'master/slave' mode in SATA, the 'found' drives will be shown on the standard POST screen as "channel#/Master" and "channel#/Slave"... If the controller is configured in either AHCI or RAID, this 'discovery' process is not done in the standard (IDE) POST - because you can't have it both ways. If the drives were discovered in both POST (IDE) mode, and AHCI or RAID mode - the board would 'think' it has two 'hook-ups' to each drive! So, after the stadard POST runs, the 'discovery' done by the 'Option ROM' is run... This, also, will 'ennumerate' the drives. It usually occurs after a 'screen clear', and will display, first, the Option ROM version information, then the 'dicovered' drives, along with their 'type', and then a "Press <some key> to configure..." message. For RAIDs, this discovery is kind of slow, as the RAID BIOS must verify the physical status of the actual stripe(s)/mirror(s)...

You may not be seeing some of this if you have the boot 'splash' screen enabled - it varies by BIOS - go into the BIOS, and on the "Advanced BIOS Features" page, disable the "Full Screen LOGO Show" item - this will allow you to 'see' more of what's going on...
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