# AHCI vs IDE



## homestyle

So what's the deal between the two?

My desktop computer in my sig is defaulted to the IDE mode. I take it's not too bad if I use mechanical hard drives, but when I update to an SSD I should change it to AHCI.

1. Can I change it to AHCI if I already installed my OS?

2. How do I know I am running in AHCI vs IDE in my laptop if I cannot go in the bios?


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## joemaniaci

info

1. You have to install AHCI drivers

2. you have to get into the bios to turn ahci on, so if you have a locked bios, youre out of luck.


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## homestyle

Quote:


Originally Posted by *joemaniaci* 
info

2. you have to get into the bios to turn ahci on, so if you have a locked bios, youre out of luck.

How do I check what mode I'm running without going into the bios?


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## savagebunny

Quote:


Originally Posted by *homestyle* 
How do I check what mode I'm running without going into the bios?

I would just boot into BIOS and check. It's the easiest and most accurate way to tell if your running AHCI or IDE


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## Pheatton

It depends on what SSD you buy. For my OCZ Vertex they state that using the Intel ICH10R controler on my board to use the default MS AHCI driver. They say you get better performance and compatibility.

Although when I switched from my RAID0 Raptors to my SSD and WD Black I noticed that the DVD drives take a long time to recognize discs now for some reason.


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## homestyle

These AHCI drivers... are these on the OS level or the motherboard bios?


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## aleiro

AHCI is faster than IDE and supports NCQ. But if your drive doesnt support NCQ it makes no sense to use AHCI. Just leave it in legacy mode.


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## aleiro

Quote:


Originally Posted by *homestyle* 
These AHCI drivers... are these on the OS level or the motherboard bios?

You will need to reinstall your OS if you switch over to AHCI. You will see posts on how to force windows to recongnize AHCI if you try to switch without reinstall but it will bring problems later on down the road.


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## joemaniaci

Quote:


Originally Posted by *aleiro* 
You will need to reinstall your OS if you switch over to AHCI. You will see posts on how to force windows to recongnize AHCI if you try to switch without reinstall but it will bring problems later on down the road.

I don't think so but it could vary from mobo to mobo. Mine for example, I am pretty sure I just need to install the drivers and activate in bios.


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## homestyle

I have the Lenovo X61T and installed an OCZ Agility 60 GB SSD.

The laptop runs fine on compatibility, but when I try AHCI, the system can't boot into windows and just bsod.

I have windows 7 32bit installed.

Any ideas?


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## BlueLights

you have to edit a few registry values before rebooting and switching to ACHI in bios, then once you've done that you boot into windows and it installs the drivers itself..or at least mine did







works fine. This guide helped me. http://www.ocztechnologyforum.com/fo...ies-*&p=442158 If I do happen to end up with problems later on, I'll just format my OS SSD and reinstall in ACHI, not really worried about it.


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## letsgetiton

Quote:


Originally Posted by *BlueLights* 
you have to edit a few registry values before rebooting and switching to ACHI in bios, then once you've done that you boot into windows and it installs the drivers itself..or at least mine did







works fine. This guide helped me. http://www.ocztechnologyforum.com/fo...ies-*&p=442158 If I do happen to end up with problems later on, I'll just format my OS SSD and reinstall in ACHI, not really worried about it.

I didn't see any AHCI settings when formatting W7. Only settings were, Install, Custom and New. I clicked custom and didn't see anything on AHCI and IDE or NTFS and FAT32. The install just started after clicking Custom.


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## Xenthos

My HDD supports NCQ I changed it from IDE to AHCI with my latest format, but I don't see any notable difference, though this doesn't mean that SSD's won't benefit from it, just my experience.


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## letsgetiton

Did you have to download a controller? I read that W7 has a controller but it's a lot slower then a good 3rd party $150 controller. I've seen Intel controllers out there but haven't been able to find any AMD controllers. That's as far as my restart gets, the MB controller screen then it keeps searching for a controller until I manually restart.
Where did you see AHCI settings at format? I clicked Custom figuring that's where I'd find some settings.


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## Xenthos

Quote:


Originally Posted by *letsgetiton* 
Did you have to download a controller? I read that W7 has a controller but it's a lot slower then a good 3rd party $150 controller. I've seen Intel controllers out there but haven't been able to find any AMD controllers. That's as far as my restart gets, the MB controller screen then it keeps searching for a controller until I manually restart.
Where did you see AHCI settings at format? I clicked Custom figuring that's where I'd find some settings.

Before I did the format/reinstall I went into the bios and changed ICH9R (my onboard controller) settings from IDE to AHCI and then I installed the OS. I didn't have to download anything since the option was already there.

Unfortunately I never checked these things out when I had my AMD computer(s).

EDIT: I don't think it's important but I did download Intel Matrix Storage manager but that was a waste of bandwidth, it only checks the drive's health status, and which SATA ports are being used..


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## letsgetiton

Quote:


Originally Posted by *Xenthos* 
Before I did the format/reinstall I went into the bios and changed ICH9R (my onboard controller) settings from IDE to AHCI and then I installed the OS. I didn't have to download anything since the option was already there.

Unfortunately I never checked these things out when I had my AMD computer(s).

EDIT: I don't think it's important but I did download Intel Matrix Storage manager but that was a waste of bandwidth, it only checks the drive's health status, and which SATA ports are being used..

Aaaaah, that could work. I thought I read, on restart from install go into BIOS and change IDE to AHCI but it makes sense to change it before hand. If it will post with AHCI enabled, it won't now. (with no controller?)


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## JessicaD

Homestyle,

When you installed Windows 7 -- what setting was your hard drive on? Was it already set to AHCI? If not and it was set up as a setting other than AHCI on installation you will need to reinstall your OS with the hard drive setting changed to AHCI.

Should you require additional assistance and guidance, Microsoft does have an official Windows 7 Support Forum located here http://tinyurl.com/9fhdl5 . It is supported by product specialists as well as engineers and support teams.

Jessica
Microsoft Windows Client Team


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## DuckieHo

Quote:


Originally Posted by *aleiro* 
AHCI is faster than IDE and supports NCQ. But if your drive doesnt support NCQ it makes no sense to use AHCI. Just leave it in legacy mode.


NCQ = BAD!

You do NOT want NCQ on desktop PC. It adds overhead which outweigh any performance benefit. NCQ benefits if you have real random access with multiple users.

AHCI should not make a HDD much (if any) faster. It does add hotswapping though.

Just a note, you need AHCI enabled + MS Default AHCI drivers to support TRIM. No other AHCI drivers support TRIM. Intel is working on it (but I don't think they released it yet).


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## letsgetiton

Quote:


Originally Posted by *DuckieHo* 
NCQ = BAD!

You do NOT want NCQ on desktop PC. It adds overhead which outweigh any performance benefit. NCQ benefits if you have real random access with multiple users.

AHCI should not make a HDD much (if any) faster. It does add hotswapping though.

Just a note, you need AHCI enabled + MS Default AHCI drivers to support TRIM. No other AHCI drivers support TRIM. Intel is working on it (but I don't think they released it yet).

But your running AHCI. (NCQ comes with AHCI which comes with the RAID installation)


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## Xenthos

Went back to IDE for my latest format, no difference in performance (NCQ was enabled on ACHI) I'll probably swap back and forth a few times with every format I do (no worries only once a week, or twice if a week has 4 days xD) and I'll probably settle with one of those.


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## joojooo

Since this thread was found via google, ...
just here to report some differences between AHCI vs IDE on win 7 64bit (using MS drivers which means TRIM is on)
Using Intel x25-m 80GB (G2),
on AHCI, Intel Toolbox doesn't allow you to run Intel SSD Optimizer (but it's ok, since OS does TRIM, you won't need to - I'd say; after a month or more I switched back to IDE so I could run it and it finished in a second as always - if there was a need to run it(meaning TRIM didn't work?), it would've prolly taken minutes)









On IDE, this is HDTune results with Intel X25-m 80G (G2):








as you can see above, the fourth core is 100% used (25% cpu usage reported since it's 4 core cpu), and ssd speed depends on the CPU speed, ie. lower CPU speed (ie. by limiting it via Power Options) means lower ssd transfer speeds(if you don't believe me ask and I'll post some screenies). The fourth core is actually used 100% due to Interrupts (as reported in Process Explorer).









Now, on AHCI, this is HDTune results with Intel X25-m 80G (G2):








as you see here, higher transfer speed and lower cpu usage(5% vs 26%) with AHCI









So, for me, AHCI for the win.

EDIT: intel x25-m 80g Postville 34nm 2.5" (INTEL SSDSA2M080G2GC) revision: 2CV1*02HD* on sata2; Controller TypeIntel PC29AS21BA0
and switching between IDE and AHCI (while windows was installed when ssd was on IDE - because due to a bios bug AHCI bios would freeze, so I had to update bios later to be able to use AHCI at all) was possible by only reboot and changing the bios setting: from IDE to AHCI and reverse (no need to reinstall anything; in my case anyways)
MOBO: Gigabyte GA-MA790FXT-UD5P
CPU: Phenom II X4 965 rev.RB-C2
OS: Win 7 64bit
mem: 4x2GB DDR3 Unganged, Dual Ch.


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## AllGamer

hmm... interesting topic, i was just debating to stay on IDE or go AHCI, having to re-install the whole OS again

it seems the results indicates it's worth the trouble of doing a clean install to use AHCI


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## plum

You don't have to reinstall.

http://www.neowin.net/news/neowin-guide-how-to-change-from-ide-to-ahci-without-reinstalling-windows

Done it before a long time ago, works perfectly.


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## AllGamer

Thanks, but no, i was not thinking about the Windows driver issues

Rather, I've already tried booting it off AHCI, and it wouldn't detect the SSD (OCZ Vertex 4 256MB), and it only sees them as boot-able if i set them as IDE in the BIOS
which is rather weird.

if i set the BIOS to AHCI and try to boot from the SSD, it just completely ignores there's a drive there, it's as if the SATA3 controller X79 doesn't even see it

still trying to figure out why.


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## plum

When you want to install your OS, take out all other drives. Leave the SSD plugged, Secure Erase it if it has data. Set AHCI in the bios and install Windows, easy.

If you can't do the above, then your drive is faulty (or something is clearly malfunctioning) and you should head to OCZ forums and bug them about it. Not much you can do that I can think of besides updating BIOS or SSD Firmware.

Getting a last gen to be detected in AHCI should be a basic thing...


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## AllGamer

update.

so in the end it was neither the drive, or IDE / AHCI setting

it was the BIOS being stupid and did not see the proper boot order of the HDDs in the rig

2x OCZ Vertex 4 256MB
5x Seagate Barracuda 3TB

so instead of following what was indicated and set in the BIOS to only boot from any of the 2 SSD
the BIOS still tried to read from the 3TB Barracudas that were formatted using GPT and of course those are not bootable

didn't help at all to reset the settings in the BIOS

the solution that worked, but doesn't make any sense is, by hot-swap un-pluging / re-pluging the SATA drives in the order you want them to boot

then the dumb BIOS keeps those undocumented "settings" for some odd logic

so, now even after i power off the machine, and power the rig back up, it keeps the order how i manually plugged in the SATA drives, even if they are out of sequence according to the ports number in the BIOS list or physical MB sata plugs.


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## drbaltazar

Window usually do this auto.if ms was to ask each time this or that you might get infuriated afteer 48 hour


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## drbaltazar

So let me get this straight :you go in bios hdd section?then plug the hd in the order you want them to start?could be wrong here but my guess is you just happened to be in the proper order needed.bios are flexible yes but they arent dynamic.bios is like a 2 year old kid lol


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## AllGamer

Quote:


> Originally Posted by *drbaltazar*
> 
> So let me get this straight :you go in bios hdd section?then plug the hd in the order you want them to start?could be wrong here but my guess is you just happened to be in the proper order needed.bios are flexible yes but they arent dynamic.bios is like a 2 year old kid lol


that's exactly why i said, it didn't make any logical sense.

normally you configure within the BIOS which HDD drive to boot from, in this case it was completely ignoring that
instead it picked up the proper order after i unplugged them and plug the boot drive back in first, then it kept the setting

i noticed the last 2 ASUS ROG MB are doing that for some strange reason

when you hit F8 to choose the drive to boot from it shows the TRUE list of drives how the BIOS will boot from
which is always different than the list that you have configured inside the BIOS in the HDD boot order screen.


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