ahci interview questions
Top ahci frequently asked interview questions
In a nutshell, I am trying to figure out for some Jetway engineers and myself, why the custom bios they made me does not allow SATA devices to boot in AHCI mode.
Obviously, this is difficult to ask considering its a *custom bios, but hopefully I can provide enough detail so that somebody could provide some ideas, because I am running out.
The board is a Jetway NF98. The original bios says American Megatrends at the top. I learned that they just provide the source code to compile (? or maybe just a logo?) but Jetway is the one who configures and produces the actual bios. So I reached out to Jetway, and they have been unbelievably helpful. I told them my goal, and they got right to it and shipped a custom bios.
The goal was simple, allow me to configure bios to refuse any other medium besides the disk connected via SATA Port 0 to be booted from. What they provided did almost exactly that, except it was not configurable, it just was set to not allow anything other than SATA Port 0 to boot.
So I plug my SATA disk in running a custom version of the Crux Linux distro, and bios reports please connect a disk, as if it sees none (even though a glance into bios settings shows a disk connected to port 0).
After some debugging I change the SATA-Mode from AHCI to IDE. This allows the disk to be seen, but boot still fails. This time it makes it a bit further, and fails when looking for root /.
To start, I have decent experience debugging Linux boot. Further, I have an exact copy (hardware & software wise) of this system, using the standard bios that came with the NF98. So I can take the disk, boot it in the standard bios, and everything is successful. When I put it in custom bios, not successful.
After further debugging, this is what I think I know:
-With sata mode as IDE
--Linux (crux) boots until looking for root
--Vista boots successfully
With sata mode as AHCI
--Linux (crux) does not boot successfully (more, the boot process doesn't start)
--Vista does not boot successfully (more, boot process doesn't start)
The Crux OS has slightly outdated custom kernel on it and uses initramfs (also custom). The Jetway engineers suggested upgrading the kernel, I thought fair enough, this did not help.
Then I figured I would try Arch Linux, which also failed in IDE mode, and wasn't seen in AHCI. This was a 3.0-ARCH kernel.
Next, and finally, I installed arch again, but this time to a single partition and used dev, not UUID or LABEL. In AHCI mode, still it was not seen. In IDE mode, still fails on transfer to root.
BUT, when I select Arch's fallback boot menu option, and SATA mode is IDE, I get semi successfully boot; that is I get to login prompt, but there is a decent amount of errors during boot. I am currently looking for what is making the difference.
My apologies for long text. Does anyone have any ideas as to why or where I should look to help figure out why the custom bios with SATA Mode AHCI does not boot?
Source: (StackOverflow)
I have installed Windows 7 on my PC (Gigabyte ga-p55-ud5) with the SATA controller set on RAID mode. After that, I've decided to try to install Mac OS X and to do so I had to set my SATA controller to AHCI.
Windows 7 only starts if I set it to RAID, Mac OS X only if I set it to AHCI.
Is there any way to let Windows 7 boot in AHCI mode without installing it from scratch?
Source: (StackOverflow)
I had a Windows 7 system working fine in AHCI mode and decided to change the motherboard to another brand. I created an image of the boot drive. I changed the motherboard which runs in IDE mode by default. Restored the image and Windows 7 boots up fine. i decided then to switch to AHCI mode.
Verified AHCI HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci is set to 0. Changed IDE to AHCI mode in the BIOS. Windows starts but it's stuck at "Starting Windows" for over an hour before I switched off the machine. I booted from the Windows DVD to get into Startup Repair option but it's also stuck in "Starting Windows" screen! I did another try to do the same but without the DVD using F8 to get the boot menu. Same result. So 3 different ways are giving a stuck "Starting Windows". I don't know why AHCI mode is causing Windows not to boot properly.
Any ideas? Is there a way to clean/remove the current AHCI installation from Windows and start a fresh AHCI installation without reinstalling Windows?
Source: (StackOverflow)
I'm sorry if this landed on the wrong stack, I'm not entirely sure if this or serverfault would be more suitable.
I have a very strange problem, when I install any iRST driver newest or older ones my DPC Latency goes through the roof and as a result all my audio is crackling and popping, whenever some sound is playing.
My PC:
- Windows 7 64-bit SP1
- P67 Extreme4
- Vertex 3 120GB
- i5-2500K
- Asus GTX 570 DIRECTCU II
- Corsair 750W AXEU
I've done a complete reinstall of windows and tested with only the iRST drivers installed (10.1.0.1008)
My second (resulting) problem is, that without the iRST drivers my boot takes about 9mins and shutdown takes a few mins too.
With the iRST I have a normal 45sec boot up.
Edit:
I should mention that the whole thing is brand new
*Edit2: *
I've noticed some problem with my USB ports too. Not sure if it is related. It takes really long times for windows to load my USB devices, be it mouse or keyboard or HDD. In BIOS the jeyboard and mouse are recognised instantly. I've ran speed test on my USB HDD's and it reports ~33Mb/s so the ports shouldn't be malfunctioning.
Source: (StackOverflow)
I am trying to help a friend with a desktop upgrade. It is an old machine with an Intel DG31 main board. The board has 1 IDE port to which a DVD-ROM drive is connected, and 2 SATA ports. 1 SATA port had a hard drive with XP on it. I have made that the secondary drive now and wiped the OS as requested, so it is just for data. The new SSD has been installed but I read that for best results one must enable AHCI in the BIOS? So I checked and in the BIOS there is a SATA Mode setting with 2 options - Native and Legacy. I think Native means AHCI? After setting to Native, I installed Windows 7 Home Premium and all the latest drivers from Intel's website and all Windows Updates. Now when I check Device Manager I see this:
Also Microsoft says HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci\Start and HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV\Start should have value 0 for AHCI but I see that the value is 3 for both. So does this mean that Native mode is not AHCI? Or Windows 7 ignored BIOS setting and installed in IDE mode, maybe because both cables are present? Please help me enable AHCI on this system. Thanks!
Source: (StackOverflow)
Which is the best setting in BIOS for SATA operation mode for a laptop to connect SATA III based fast SSD drive, and why?
- ATA
- AHCI
- RAID On (Intel Rapid Storage)
There will be no RAID set in system (laptop with 1 drive slot only). I've read that "RAID On" enables AHCI anyways but would prefer some confirmation that one is better then the other.
For the sake of example the laptop I'm talking about is a Dell Latitude E6420 with an Intel Core i7-2720QM, 8 GB of RAM and an aftermarket SSD, an OCZ VTX3MI-25SAT3-240G Vertex 3 MAX, which will replace other standard drive that's inside.
But this questions is asked as general for future reference.
Some reference: How to configure the BIOS for RAID or AHCI on an Intel® motherboard
If you are using a SATA hard drive, set your BIOS to RAID mode. RAID mode provides the greatest overall flexibility and upgradeability because it allows your system to be RAID ready and enable AHCI.
Source: (StackOverflow)
I had my drive controller configured for IDE when I installed Windows 7. This didn't change when I upgraded to Windows 8.
I now need to enable AHCI, but doing so causes Windows to fail to start. It doesn't know how to automatically fix the problem.
I was able to use Regedit from the recovery area, in order to try using this fix that worked for Vista. That key is missing in Windows 8, however.
I read that the relevant key is now in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\storahci. But my settings already match the changes they suggest making.
How can I get Windows to boot after enabling AHCI in the BIOS?
Source: (StackOverflow)
I've noticed in the BIOS settings of the newer PCs I own that I can configure the drive controller work either in AHCI (Advanced Host Controller Interface) mode, or else in IDE mode.
I'm suspecting that AHCI "performs" better, but I really don't know much about that from a practical standpoint. However, I've also noticed that certain programs (e.g. Ghost 2003) simply don't detect my hard drives if I choose AHCI mode. (AHCI = A Heck of Compatibility Issues?)
So ... why does AHCI exist, why should I care and want to use it, and why/when should I not want to use it? Are there features of newer hard drives that require AHCI, and do they otherwise dumb themselves down when running in IDE mode?
Source: (StackOverflow)
I have a Shuttle Intel G31 + ICH7 (base -- not M/R etc) system. I just bought an OCZ Vertex 3 120gb [VTX3-25SAT3-120G] which includes the Sandforce 2218 firmware.
The ICH7 does not support AHCI. I understand that this can be a problem. What I don't understand, is if it's necessary to have the proper performance of this drive. I know that without AHCI I may get a limited read/write speed -- this is fine. What my concern is, is the constant freezing/hangs I'm getting with Windows 7 on any disk activity. The 'Highest Active Time' flip-flops from 0 to 100% every minute or so regardless of large or small files.
EDIT: The threads/processes with the highest response time is the kernel.
I've been reading about other people with Shuttle SG31G2s, and they seem to be using SSDs no problem. Is this the controller's fault? The fact that I do not have AHCI enabled? It makes sense to me that if this SSD requires AHCI features that it would cause Windows to hang, but I would like to fully determine my situation before returning things/reformatting.
To initially have my drive recognise the SSD at all, I had to change the BIOS option to Force Gen II instead of Auto for the SATA controller. I then installed Windows with no problem. There were no errors in the event log related to disk usage, but watching the perfmon I could see the highest active time and the processes (usually pagefile.sys being written to, or chrome/firefox caching) which was correlated to the hanging.
So now what I need answered is: should I be returning this SSD and getting one with a different controller, or returning the SSD all-together as it will never work out and I will continue to get these hangs.
Posts I've read:
Windows 7 New SSD SATA AHCI? -- suggests to use AHCI
http://forums.anandtech.com/showthread.php?t=2189868 -- Sandforce issues
Windows 7 freezes with SSD -- and attached posts
Why does my Windows 7 PC / SSD drive keep freezing? -- this is not the controller I have, but still a related issue.
Windows 7 hangs after longer inactivity of user -- also tried messing with power settings with no luck. It was already set to 'Never' for turning off HDDs.
Source: (StackOverflow)
What is the relation between AHCI and SATA? How come an OS cannot operate a SATA controller without an AHCI driver, while the BIOS knows how to boot of a SATA hard disk?
What are the difference between the SATA controllers, so that they need a specific AHCI driver?
Does the BIOS has a "driver" inside to operate and boot from a SATA(in AHCI mode) HDD?
Source: (StackOverflow)
Foolishly, I installed Windows 7 with my new SSD set to IDE. I would like to change it to AHCI. I have done this before, with a different motherboard.
What happens:
- I set the controller to AHCI in the BIOS; I also check correct boot order
- On boot, I get the 'BOOTMGR not found' error
- I use the Windows Recovery Console on the DVD
- Diskpart etc can see the disks, and bootrec claims to have rewritten the MBR/bootloader
- I reboot, same problem
- Recovery Console again and it detects a problem, fixes, reboots
- Recovery Console again and it detects the OS, and a problem - fixes, reboots
- I ignore the 'press any key to boot from DVD' prompt
- Windows boots fine
- I restart without the DVD and I'm back to square one
That optional 'press a key to boot from DVD' stage is something that the recovery process introduces - normally you have to choose to boot to the DVD at the BIOS stage. You also see this when installing Windows. I suspect that whatever temporary state that is is compatible with AHCI - but not the standard it returns to.
I have done the msahci/iaStorV registry hacks to no avail (this worked with the previous board). I can put it back to IDE where normal service is resumed. The board is an Asus M5A99X, the southbridge is AMD SB950, and this is Windows 7 x64. I would quite like not to have to reinstall it again.
Any ideas as to what I can do as a permanent fix?
Source: (StackOverflow)
Here is something that has been bugging me for a long while. Modern chipsets support AHCI for hard drives which amongst other things is supposed to support hot swappable drives. In Windows this means you can plug a drive in any time and use it. The flip side is you should be able to unplug it anytime after dismounting it (Safely Remove Hardware).
But so far I have only had this successfully work with nVidia chipsets (nForce4 mainly) and some JMicron SATA controllers. On Intel chipsets I can plug a drive in but it never shows up in the Safely Remove Hardware list in Windows. And just un-pluging a drive can lead to all sorts of nasty problems.
Note that I always install the Intel drivers rather than using the Microsoft drivers and I have tried this using Server 2003/2008, Vista & 7.
So does Intel (ICH9/10) chipsets properly support hot swappable SATA?
Source: (StackOverflow)
I have switched SATA controller mode from IDE to AHCI, and my Fedora (the latest release) doesn't boot now. I'm not surprised by this fact alone, but I am surprised with the message I'm getting:
BOOTMGR IS MISSING
Which, I believe, is BIOS message, not OS message, so Fedora doesn't even start booting (unlike Windows).
Why am I'm getting this message, and is there any way to enable AHCI without reinstalling Fedora from scratch?
Source: (StackOverflow)
I've been using a Vertex3 SSD as my Windows 7 boot drive in IDE mode for a few months without problems with a ASRock A75M-ITX motherboard.
Today, I ran the Microsoft fix-it to enable the AHCI drivers, changed the SATA controller to AHCI mode in the bios, and rebooted. It gave me the message
BOOTMGR missing. Press CTRL+ALT+DEL to reboot
So I went back to the BIOS and saw that my SSD is no longer listed in the boot priority menu. However, it shows up and boots fine if I press F11 to bring up the boot menu during the POST and select it. The first time I did this, Windows told me the AHCI driver was installed and I should reboot.
Currently my computer is usable, with all indications that the SSD and Windows are working properly in AHCI mode, but the drive will not show up in the BIOS boot priority listing, although it is listed elsewhere correctly. I failed to find any BIOS updates for my motherboard on google.
Is there something else I can try?
Source: (StackOverflow)