Processors

Quick Tip: Improve your SATA disk performance by converting from IDE to AHCI

In this Windows Quick Tip, Jack Wallen shows you how to improve the performance of a SATA hard drive using a Windows Registry tweak.

Most modern computers take advantage of the Serial Advanced Technology Attachment (SATA) hard drive interface. There are plenty of reasons why this is so, and most administrators know that IDE is no longer considered a standard for hard drives. What many administrators do not know, however, is that for maximum compatibility, most PCs are set up to use the older IDE interface. Because of this, when you install Microsoft Windows on a machine it may recognize only the BIOS IDE setting and enable IDE-only at the registry level. This can, in some cases, decrease the performance of the PC.

Fortunately, there is a way around this that isn't all that difficult, and it will not require you to reinstall Windows.

This blog post is also available in PDF format in a TechRepublic download.

First I want to make the usual disclaimer: You will be editing your registry and possibly changing your BIOS's settings. As there is always a risk when making changes to either of these, please make sure you know what you are doing before you attempt this and make sure you have a solid backup of your system (just in case). With that said, let's dig in.
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Edit the registry

Open up the Registry Editor by clicking Start | Run in Windows XP or by typing "regedit" in the Desktop search box in Windows Vista and 7, and then type or click regedit to open up the registry editor. When the registry editor is open, navigate to this key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci

Once there (Figure A), you will see the Start key, which is the key you need to edit.

Figure A

Before you start modifying your registry, you might want to make a backup copy of that registry -- just in case.
Right-click the Start key and select Modify. When you do this, another new window will open (Figure B). This new window contains all the data for the Start key. What you want to edit is the Value Data. Most likely your Value will be set to "3." You want to change that to "0" (no quotes).

Figure B

Make sure you change nothing but the Value Data.

Once you have made that change, click OK. You can now close the Registry Editor.

Reboot and BIOS

The next step is to reboot your machine and then enter into the BIOS. Since every BIOS is different, all I will say is that you need to enable the AHCI setting in your BIOS. When this is complete, allow your machine to reboot and hopefully you will enjoy a boost in performance. I say "hopefully" because not every machine will see a marked improvement.

What about RAID?

If your machine happens to use RAID, you need to repeat the same steps with only minor changes. During the Registry Editor phase, you want to look for either:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStorV

or

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStor

Once you have located either of the above, make the same change you did for the Start key and reboot your machine. You will still need to make the change in the BIOS as well, before the change will actually work.

Final thoughts

Hopefully you will find this gives your machine a performance boost. If the gains are minimal (or nonexistent), then no harm no foul. If you are unsure if any gains were made, put your machine through a test that pushes disk I/O to the limits and see if the performance has improved.

About

Jack Wallen is an award-winning writer for TechRepublic and Linux.com. He’s an avid promoter of open source and the voice of The Android Expert. For more news about Jack Wallen, visit his website getjackd.net.

97 comments
riggy001
riggy001

WOW! I changed the appropriate regedit value to zero, then rebooted and entered into BIOS and found the SATA values and changed it from IDE to AHCI. When windows came back online it told me I needed to reboot, and so I did, and WOW! It halved the time to be up and running again! Why is this not the default? I have been running this slow for 2 years! I think it also fixed my video stutter with Media Center (Whenever I used to watch TV and run Firefox the video would stutter and skip, but it isn't doing that now, the TV stream is seamless). (I use my SATA (1TB) drive for my "recorded TV folder", and I assume that is the drive on which the 30-minute buffer is recorded, and the C-drive is where the OS and MCE live.) If, after a week, I get no jitter, skip, pause, or other video defects while browsing while watching live TV (which I do every day for several hours a day), then I will geek this solution to every forum to which I have sought an answer to this problem.

ZoltanZ
ZoltanZ

I am partially confused here .. I have a brand new Dell with Intel chip and motherboard and a 1TB SATA SG Hard Drive. Looking at the first registry Start setting in the article I have a 3 instead of 0 ... If I look at the second and third (iaStor and iaStorV) registry items (I have both not either/or) the iaStor shows 0 in the Start option and the iaStorV shows 3 in the Start option. Going to the BIOS the setting for the Hard drive indicates only two options ... RAID and ATA for the SATA Drive .. which is currently set at RAID... So is there anything that has to be changed in the settings? Such as the iaStorV Start set also to 0 or leave it at 3 ???

mthaler
mthaler

I have not been able to get this to work with my AMD based motherboard (Asus M4A87TD). I get the BSOD. I made sure the AMD drivers are installed, and I even tried pointing the line in the msahci "imagepath" registry entry to point to the AMD driver instead of the default Microsoft one. Has anybody gotten this to work with this chipset?

ilya.shick
ilya.shick

This is only small portion regardingthis issue. Dell OptiFix after registry modification no way to run AHCI on Windows 7. Accoring to Intel ro run Intel Matrix but only F5 during intalltion.Every time is Blue Screen. Durign reaseach found the latest Dell matrix published on November must be run to support ACHI.Bur is a very tricky. W7 System Manager needs to port address to proper run .inf and in Windows7 subfolder. Before do it download Intel ChipUtil325 to see a details anf get proper inf. file. After all modify BIOS check ACHI

bigpygme
bigpygme

had no driver in Win7 x64 for my M4A89GTDPRO/USB3 mobo. ASUS sent me a link, it was listed as a Utility update. I can provide it if anyone else needs it. But i am not sure where the driver goes ... ASUS said, path = RAID>AMD>Driver>Disk>AHCI, but i don't know what the root is, and can't find this path. anyone else know? I hope this AHCI driver install DOES speed up the HDD, it's been some work to get to this point and get it installed (when i finally do) ...

dukker
dukker

Made Change on my NetBook with SSD. Made it anew system. Thanks

Gis Bun
Gis Bun

No offence to Jack, but he tends to do a lot of "reporting" on Linux and open source subjects. I would really verify how valid this option is and whether it's reliable. Judging from the BSOD and other issues, I would hold off in touch it. I suspect if it works on some and not on others, there is probably some type of incompatibility.

GreatZen
GreatZen

According to OCZ: "AHCI AHCI is not official supported on OCZ SSDs and may under some circumstances affect performance, specifically during windows installation. Enabling AHCI can result in higher performance in synthetic benchmarks for SSDs and HDDs alike, but can cause hang-ups and intermittent freezes in SSDs since it allows multiple access requests to compete for a drive that is not made to address re-ordering of commands in the queue. We recommend AHCI is set to disabled in both Windows and in the BIOS. Native Command Queuing greatly increases the performance of standard rotational drives but it has no bearing on SSDs." The issue is that NCQ (a feature of AHCI that among other things reorganizes requests into an order more conveniently accessed by the drive head), reorders the drive requests on a drive that doesn't have a drive head, and uses a different caching system. Apparently the illusory improvements for enabling AHCI on SSDs is a result of most benchmarks still not being multi-threaded.

Who Am I Really
Who Am I Really

in the BIOS of my system there is a warning changing this setting to AHCI may require re-installation of the OS

K7AAY
K7AAY

This causes 32-bit Ubuntu 10.10 to fail.

dl
dl

This sounds promising but for one serious Catch 22. As far as I have been able to find out, the only way to install the SATA drivers with AHCI is when you install Windows XP -- using the F6 key early in the process to allow installation of 3rd party drivers. Despite searching far and wide, I have never found a substitute for this. So I am most curious how we're supposed to install these drivers. I have a floppy I made from my Asus motherboard's installation CD for installing the drivers. Is there a specific place to install them? I installed Window XP SP2 before AHCI became available and the new motherboard I bought did NOT require a reinstall of Windows XP when upgrading from my previous mainboard -- which is precisely why I bought it. Hence my question.

steveh
steveh

I just checked out the Registry in my Win 7 64 bit VM and saw that I could make that change but, since this is running inside my Ubuntu 32 bit O/S, I'm wondering if: A) There would be any improvement? B) If changing the BIOS would negatively impact Ubuntu? I know I could test this myself but, since it's my primary system, I'd like to not go playing with a working system if someone else either knows or would be willing to test and see if works.

mikedav
mikedav

I have a SATA HD Seagate Momentus 5400.3 ST980811AS - Hard drive - 80 GB - internal - 2.5" - SATA-150 - 5400 rp installed on my XP Dell 1520 Laptop. The section of the registry doesn't exist. Can I create and it will work? Thank you, Mike Davies

mfrantz
mfrantz

I have a controlset 1 through 5 and find the start key in two of these. Which one do I edit and why do I have so many?

bigpygme
bigpygme

i have posted just above you, have an ASUS M4A89GTD PRO/USB3 MB, and maybe this tip that just arrived as a reply will help you. i'm about to try to use it as a guide, though the files aren't for an AMD setup, they're for Nvidia ... UPDATE: this setup didn't work for me. i put the .sys driver in system32>driver folder and the other two in system32. maybe you'll have more luck. or maybe we need a better clue on DRIVER PATH for AMD. SECOND UPDATE: now Asus says that AHCI drivers need to be installed at the same time the Win7 OS is installed. How was i supposed to know that? and why do they have the AHCI drivers available as a utility download if you can't use them to update to AHCI drivers? grrrrrrr ... File Locations from Another Post: Based on what I see when I go into Device Manager in Windows 7 and look up the drivers for the NVIDIA nForce Serial ATA Controller (obviously my motherboard, the M4N72-E has NVIDIA rather than AMD chipsets), the AHCI files are located in two directories. nvstor32.sys is in the c:\windows\system32\Drivers directory. All of the other files aer in c:\Windows\system 32. I hope this helps. I know that with Windows XP you had to install the drivers during installation of Windows XP -- I have yet to find a way to install them pro-install. I would strongly suggest that you create a clone of your hard drive BEFORE you try installing the AHCI drivers -- it is possible that attempting to install them could make your Windows 7 inaccessible. And, of course, after installing them be sure to go into the BIOS and change the configuration for your hard drives to AHCI from IDE. Good luck. Please let us know how this turns out and your step by step procedure. Posted: 12/11/2010 @ 08:49 AM (PST) dl@... Job Role: Executive Manager (Chairman, CEO, CFO) Location: River Forest, Illinois Member since: 02/06/2006

dl
dl

Based on what I see when I go into Device Manager in Windows 7 and look up the drivers for the NVIDIA nForce Serial ATA Controller (obviously my motherboard, the M4N72-E has NVIDIA rather than AMD chipsets), the AHCI files are located in two directories. nvstor32.sys is in the c:\windows\system32\Drivers directory. All of the other files aer in c:\Windows\system 32. I hope this helps. I know that with Windows XP you had to install the drivers during installation of Windows XP -- I have yet to find a way to install them pro-install. I would strongly suggest that you create a clone of your hard drive BEFORE you try installing the AHCI drivers -- it is possible that attempting to install them could make your Windows 7 inaccessible. And, of course, after installing them be sure to go into the BIOS and change the configuration for your hard drives to AHCI from IDE. Good luck. Please let us know how this turns out and your step by step procedure.

Justin James
Justin James

... won't have any effect with SSDs. None at all. J.Ja

EubieDed
EubieDed

Unfortunately having an SSD as the boot/Win drive results in a boot failure if AHCI is enabled for other drives. Unfortunately the BIOS on my machine does not let me distinguish between the drives which support AHCI and those which do not. Too bad, because the POST ran much faster with AHCI - until it halted with the boot failure, that is.

dl
dl

As best I understand it, if you have Windows XP installed and did not install the AHCI drivers during installation of Windows XP, this message is accurate. Under these circumstances, if you switch the SATA mode in BIOS to AHCI, you will get a BSOD when you boot. If you have Windows 7, you don't have to worry about this since Windows 7 has AHCI drivers built into it (I think the same is true of Windows VISTA, but I can't vouch for it.) With Windows XP, the catch is that you've got to install the AHCI drivers from your motherboard manufacturer early in the Windows XP installation using the F6 key. The CD that comes with Asus motherboards, for example, usually includes a choice to make an installation floppy for the AHCI and RAID drivers. Shortly after the Windows XP installation starts, you get a chance to hit Function Key 6 to install third party drivers. You're told to insert the floppy and the floppy's contents are copied to the hard driver or RAM for use in the Windows XP installation process. That's why I posted the comment here about a Catch 22. I hope this is helpful.

bruceslog
bruceslog

Um. yeah. Could you post the registry entry that you changed in your Ubuntu system so I can see it, please ?

ultimitloozer
ultimitloozer

is pretty much the same for any hardware. Put in the media, run the installer and follow its prompts or right-click the .inf file and select Install from the context menu if there isn't an installer. Done. Drivers have been installed.

dl
dl

I think the article is incredibly misleading. The author seems to assume that the proper drivers and controllers are installed on your computer so that all you have to do is change some registry entries. In the interest of fair play, may I suggest that the author state up front that the proper drivers and SATA controller must be installed first -- otherwise there's nothing you can do in your registry (and BIOS) to activate AHCI. If you set you BIOS to AHCI and haven't installed the proper SATA controller, you'll get a BSOD -- which will, of course disappear when you reset your BIOs setting for your SATA drives back to IDE mode. Actually for most of us with Windows XP, the issue isn't SATA drivers, it's the Serial ATA Controller which, as best I can determine, must be installed with Windows XP (using the F6 key for 3rd party drivers). For Asus mainboard with NVIDIA chipsets, this appears to involve installing 1 file in the c:\windows\system32\driver directory about 20 files in the c:\windows\system32 directory -- plus gosh only knows how many registry entries and what they are.

ultimitloozer
ultimitloozer

This will not affect anything running in a VM since it does not have direct access to the hardware.

ultimitloozer
ultimitloozer

You need to install the proper hardware drivers which will also create the necessary entries in the registry. You may need to enable the driver after installation since the system will not immediately recognize SATA drives as being attached since the SATA controller is probably in IDE mode.

ultimitloozer
ultimitloozer

The change needs to be made in CurrentControlSet (not one of the numbered ControlSets).

moredata
moredata

My registry key was set to 3 and I changed it to zero. Rebooted, entered Bios and looked everywhere for enable AHCI option. I only found a setting called: Onboard SATA mode that was set to Native IDE. There are only 2 options for that: Native IDE and RAID controller. Does this mean my Bios doesn't support AHCI? I am using a SATA hard drive, BTW.

dl
dl

Since your earlier post where you asked these questions is at its limit, I thought I'd answer here. The questions: "some Questions - did you have to use the reg tweak that started all this to get your AHCI operating? did you install your OS on your own, or was it pre-installed? did you have to load the drivers, or was it automatic with the install? and where are the AHCI drivers found in your OS, if you know?" I did not have to use the registry tweak to get the AHCI to work. I installed Windows 7 myself -- I've built about 70 computers over the years for my own small office and even for some law clients. With the two Windows 7 installs I've done so far (one 32 bit, one 64 bit), the AHCI installed as part of Windows 7 -- I did not have to add the drivers during the install. I can't imagine you'd have anything to lose if you were to add the drivers during the install or reinstall. NVIDIA nForce Serial ATA Controller (obviously my motherboard, the M4N72-E has NVIDIA rather than AMD chipsets), the AHCI files are located in two directories. For the NVIDIA drivers on my Asus motherboard, nvstor32.sys is in the c:\windows\system32\Drivers directory. All of the other files are in c:\Windows\system32. I think a repair install would enable you to load the drivers you got from Asus. Given how much more quickly and smoothly Win7 installs than WinXP, it's probably worth doing this -- after cloning your hard drive as a safety measure. If you don't have a spare hard drive, they are really inexpensive now -- 1 GB SATA drives tend to sell for $59 to $99 these days (newegg.com, microcenter.com, frys.com).

bigpygme
bigpygme

i greatly appreciate the time you took to look at device mgr and your file set up. i tried an analogue to what you described - i downloaded the AHCI drivers from Asus, put the .sys file in system32>Drivers, and the other two files into system32. then switched BIOS settings to AHCI and tried to boot. sadly, no go. i guess the AMD settings will be different. if i hear back from Asus, i will post the solution. but thanks for your time for trying.

ctrogers
ctrogers

"won't have any effect with SSDs. None at all." I wouldn't make such a blanket statement. There are a few sites with benchmarks showing gains (up to 3x performance) in small reads when using AHCI on a SSD. For instance: http://www.pcper.com/article.php?aid=669&type=expert&pid=3 Even more gains are to be made when running several processes reading from the SSD at the same time. Note that this does require a SSD that actually supports NCQ, and the cheapest SSDs do not. My own system showed an even greater improvement, but I will chalk that up to an incompatibility of some sort that using the AHCI drivers cleared up.

ctrogers
ctrogers

I had the same boot failure after initially setting the bios to AHCI. The fix was to set it back, make the windows registry change as in the article, then set the bios to AHCI. As to SSD drives not supporting NCQ- that varies based on the drive and firmware. My Intel G2 SSD had very poor performance worse than a standard hd before I enabled AHCI (maybe a motherboard issue?), now the performance is up to spec after enabling it.

Who Am I Really
Who Am I Really

to change the drivers in XP from IDE Mode to AHCI is to use a product such as Backup Exec and do a "bare metal recovery" from a backup base image when the recovery environment loads it also asks for F6 to install RAID/SCSI controller drivers and it will insert those drivers into the OS during the restore process

bigpygme
bigpygme

doesn't seem like the AHCI dirvers are installed on my Win7 x64 OS, because i can only run IDE. you sure they're already there? wonder why my Win7 OS can't or doesn't find them ... thanks for any help, Michael

dl
dl

I have tried (on a cloned drive) the approach you have suggested and it does not work with Windows XP. I tried it a few years ago and again this week. I fully understand we're talking about hardware when it comes to a controller (I've built or repaired 70 Windows computers -- so I'm I know a enough about computers to be dangerous). But the catch with Windows XP seems to be that you can install the software that will allow AHCI mode to be used only during the installation of Windows XP by using the F6 key early in the WinXP install process. This is what every online article of this issue has made abundantly clear until this article. Now this article implies you can simply activate AHCI with a registry edit and change in the BIOS. The misleading aspect is that the author failed to specify which versions of Windows this technique would work in. He should have noted that it will not work in Windows XP, still used by 51% of the world's Windows computers. Has anybody here actually made use of AHCI mode possible on a Windows XP computer (originally installed before Service Pack 3 became available) following the approach suggested in the article or in the posts in this thread? If so, please reply with a step by step of what you did and the motherboard you used. I can tell you that with Asus motherboards like the M4N72-E and M3N78-VM, you must use a floppy created from the CD that accompanies the motherboard to install the software needed for AHCI mode to work. The motherboard has the proper controller -- but this software must be installed during the Windows XP installation (it's not needed for Windows 7). If you've found another way to do it, please share it with us. I'm frustrated by the imprecise writing in the IT press, especially online. It's obvious there is no fact-checking and not a lot of editing done. And I am tired of the snotty posts where some writers (safe in their anonymity) go out of their way to insult the intelligence of others (honest, it doesn't make you appear any smarter to insult others who post here or anywhere else). The idea is for us to be helping each other, not insulting one another. Perhaps we could all start acting like adults.

ultimitloozer
ultimitloozer

After all, the title indicates it is about improving the performance of SATA drives, therefore you must have a SATA controller (which is hardware - you seem to believe it is software) and SATA drives installed in your system. Really, if you don't have a SATA controller, how did you manage to connect the drives to the system? The author probably should have mentioned the exception with XP, but he was probably using Vista (yeah, right) or Win7 when he did this and both of them already include (and install by default) the MS AHCI drivers. These will allow the base ACHI functionality with most controllers & drives. In order to obtain the best results, you should use the drivers provided with your system/motherboard, especially for RAID configurations. If these drivers are not provided with an installer, you can just right-click on the .inf file and select the Install option from the context menu which will install the necessary files to the proper locations and create the required registry entries. You do not need to manually play with any of this, even with XP as you seem to be insinuating.

owner
owner

So where do you get the drivers? I have Win7 64bit and had an issue where it said there was an error loading the OS.

marym
marym

AMD Athlon 6150LE chipset. No option in BIOS except to enable or disable SATA 1 Controller.

rpr.nospam
rpr.nospam

http://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface explains operating modes of SATA controllers . The page references http://www.intel.com/support/chipsets/imsm/sb/CS-015988.htm which says that enabling RAID mode on Intel motherboards (and MBOs using an Intel chipset) also enables AHCI mode. I've just had a look at BIOS of a HP desktop (with the AMD 780V chipset) and it has the following SATA modes in BIOS: - Legacy IDE mode - Native IDE mode - AHCI RAID -> choose this one -- rpr.

bigpygme
bigpygme

i decided too much could go wrong with a repair install to bother with it, just to get the benefits of AHCI. maybe i'm wrong and it's actually no trouble and no loss, but the repair install guide from M$ indicates you can lose drivers, settings and all kinds of things on a repair install of Win7.

dl
dl

My head continues to spin with all the contradictory advice, but having spoken with Asus tech support on other matters (it's so nice that their tech support folks are in Indiana), I'd be inclined to listen to them. If they say you can installed the AHCI without a repair install, try it (but first clone your hard drive and try it on the clone -- just be protected -- I'd hate to see these experiments put your computer out of business). Let us know what works for you and when you do, please specify the model of your Asus motherboard (I realize you posted it before, but this would make it easier for anybody who stumbles upon this thread). Good luck.

bigpygme
bigpygme

thanks for the time and benefit of your experience ... i'm a DIY'er (but just for me), so i did build this and installed Win7 x64. Odd to me that Win7 is not operating with AHCI natively, based on what you said. Asus said a Repair install won't work for installing the AHCI drivers, but since you and someone else think it would, i am willing to give her a go. i have image backups, so i'll be ok if things go awry.

bigpygme
bigpygme

thanks lots for your help with Win7 Repair Install. i know i could've found it on M$, but you've given me other good resources. and my head's spinning too, as i am mystified by why some Win7 machines apparently have AHCI natively and others (like mine) don't seem to. some Questions - did you have to use the reg tweak that started all this to get your AHCI operating? did you install your OS on your own, or was it pre-installed? did you have to load the drivers, or was it automatic with the install? and where are the AHCI drivers found in your OS, if you know? thanks for reaching out to help !!! Michael

dl
dl

My head is spinning from all the contradictory information. I can personally testify that I installed Windows 7 on 2 computers so far and did not have to use third party drivers for AHCI during the install -- both on Asus motherboards over a year old. I'm writing this on one of them now and AHCI is working just fine. I did notice, however, that during the Windows 7 install process there is an opportunity to add third party drivers -- it's when this screen comes up that allows you to format, etc. -- look for the little icon and label "Drivers." I would imagine that a repair install in Windows 7 works pretty much the same as in Windows XP. You'll find instructions at: http://www.sevenforums.com/tutorials/3413-repair-install.html http://forums.techarena.in/operating-systems/1141542.htm I hope this helps.

bigpygme
bigpygme

if it's true that AHCI driver(s) are built into Win7, then i would be able to use the reg tweak to switch from IDE to AHCI - but i can't. Asus pointed me to a MB utility download page for the AHCI drivers, which i did - then a week later (yesterday) came back and said they'd have to be part of an initial install of Win7. they won't work by just adding them now, post-install, so says Asus. so, in my experience, i'm not at all sure that AHCI is preloaded in Win7 OS. it certainly hasn't worked for me ... i don't know if a Repair install would allow them to be installed, and am fuzzy about Repair install on Win7 anyway - on XP it was easy. any idea whether a Repair install would work?

dl
dl

Despite what some folk have suggested here, as best I can determine the only way to install the AHCI ability is during the installation of the Windows. I know that with Windows XP this is definitely true. Very, very early in the install you have to hit Function Key 6 to tell the process that you wish to install third party drivers. You'll need a floppy disk created from the Asus CD that came with your motherboard - or perhaps just copying all the files from that file you got from Asus. Having recently installed Windows 7 on a few computers with Asus mainboards, I found no need for the floppy -- AHCI seems to be built into Windows 7. Several people here have insisted that you can add AHCI post-OS installation, even in Windows XP. Yet as far as I can tell, nobody has posted here how they've actually done this in Windows XP. I tried to do it on a clone drive and it bricked Windows XP. I've built only about 60 Windows computers, so I'm not as well versed in all this as some who post here -- so if they have a solution that they've actually used, it would be helpful to provide a step-by-step procedure in plain English that all could understand.

ctrogers
ctrogers

That's a well reasoned argument and after a lucky google search, I think I've found the answer here: http://techreport.com/articles.x/15433 "According to Intel, its SSDs are so fast that NCQ helps to compensate for latency encountered in the host PC. Even today's fastest systems take some time (time is relative in the microsecond world of the SSD) between when a request is completed and another one is issued. Queuing up multiple requests can keep a solid-state drive busy during this downtime, and the X25-M is capable of stacking requests 32 deep."

Justin James
Justin James

""won't have any effect with SSDs. None at all." I wouldn't make such a blanket statement." I will, and do. Why? Because what ACHI mode does, is enable Native Command Queuing, which affects how the head of the drive is moved as data is read off the platter. Since SSDs don't use moving heads, there is no benefit to ACHI. Any benefit you *are* seeing is (in my guess) a result of different drivers being loaded as a result of the switch. J.Ja

bigpygme
bigpygme

msahci.sys is right where you said it would be, right on, but my Win7 x64 machine still will not boot when i change from IDE to AHCI. i have downloaded my specific (Asus M4A89GTDPRO/USB3) MB drivers, but Asus' directions on where to put them are unclear. what path did you use for your MB specific drivers? do they just go in the system32->Drivers folder?

ian
ian

I have a win 7 pro x64 the drivers are installed - C:\Windows\System32\drivers\msahci.sys I too have an Nvidia chipset but I only see nvraid.sys and nvstor.sys. I do not see nvrd64.sys or nvstor64.sys. I am not running any sort of raid configuration yet, I just have two sata drives connected to the mobo and an external usb backup.So not sure which drivers should be present. The PC came ready installed with Vista x64 and a sata internal drive but the registry was set to 3, which I changed to 0. The bios does not give an option of AHCI. Do I need to upgrade the bios or mobo drivers to get this option?

ultimitloozer
ultimitloozer

If you have the registry entries mentioned in the article, the drivers will be there. If you don't believe it, look in C:\Windows\System32\drivers to find msahci.sys. The RAID drivers are vendor and chipset specific. For example, my MB uses an NVIDEA chipset and utilizes the following drivers: nvraid.sys, nvrd64.sys, nvstor.sys and nvstor64.sys.

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