How important is AHCI?

[mendopaul]

I've just loaded Win 7 on a new machine with the OS on an Intel X-25 SSD and two other Sammsung T1's for storage. I didn't know to activate the AHCI capability when I did the install. Intel support is telling me that the only way now to get AHCI is to reinstall the OS after selecting AHCI in BIOS. How valuable or important is it to have the AHCI capability? Is this only for the SSD, or will it also work with the rotating hard drives. Thanks for your thoughts!

 

[smarteyeball]

For optimal SSD performance, future firmware updates etc - it is important.

However Intel is incorrect about re-installation - AHCI can be enabled after the OS has already been installed in a different mode:

http://www.sevenforums.com/tutorials/61869-ahci-enable-windows-7-vista.html

Your other drives will still function normally as well.

 

[fseal]

I switched to AHCI after OS install with no problems.

It will allow multiple threads to read/write to you drive "at the same time" whereas the IDE mode is only a single thread. This increases your read/write throughput DRAMATICALLY.

 

[xxxdannyxxx]

I changed mine with the os installed using this tutorial

http://www.sevenforums.com/tutorials/61869-ahci-enable-windows-7-vista.html

 

[joema]

I did some perf. tests with AHCI on and off, and couldn't tell any difference. That was about a year ago.

If you have a SATA optical drive, enabling AHCI may prevent it from working properly. This varies based on drive, firmware, motherboard and BIOS. More info:

http://www.sevenforums.com/hardware-devices/48003-lg-optical-drive-wont-burn-dvd-ahci-mode.html

 

[pparks1]

I ran for quite some time with my Intel X25-M G2 in IDE mode. There was an 8 second delay on boot from my gigabyte motherboard when I was in AHCI mode. I honestly felt that I didn't gain back enough in performance to compensate for the 8 second loss on each and every boot. I was unable to find any difference really between AHCI and IDE mode in all of the time tests and such that I did.

Later, Gigabyte released a new BIOS update which reduced that 8 second delay down to around 2 seconds...so at that point...I switched over the AHCI mode as it's better in theory.

But I wouldn't worry much if you are using IDE mode. It's unlikely to be a noticeable change.

 

[James Colbert]

I successfully used the process linked to by earlier posters to enable AHCI in Vista (some time ago). I didn't really notice a significant performance gain, but the reason I enabled it was to gain Hot Swapping for my sata drives, which works like USB. Great for backing up partitions and the like for use as offline storage, restoring old files, working on ongoing projects that don't need to be constantly online, etc. As for Win7, AHCI was enabled when I installed. I believe hot swapping works for SSD as well (just not the boot drive...).

James

 

[FliGi7]

So, if I have 4 sata drives (Win 7 OS, Win XP OS, Data, and Backup drive) and 2 sata optical drives with SATA currently set to IDE and I do the change in Windows 7 to make the Windows 7 drive AHCI, all of those other drives will still operate fine? I'm hesitant to make this change, given the possibility the optical drive may not function well and I believe I'd have to re-install my XP OS after this change, correct?

 

[James Colbert]

So, if I have 4 sata drives (Win 7 OS, Win XP OS, Data, and Backup drive) and 2 sata optical drives with SATA currently set to IDE and I do the change in Windows 7 to make the Windows 7 drive AHCI, all of those other drives will still operate fine? I'm hesitant to make this change, given the possibility the optical drive may not function well and I believe I'd have to re-install my XP OS after this change, correct?

That is correct. All of your drives will operate fine. No reason to worry at all. As to your question regarding XP, here is a google list of articles that should be informative:

AHCI xp - Google Search

James

 

[FliGi7]

That was always a worry of mine in just flipping the switch on AHCI that I certainly could/should read up on but just haven't yet. Thanks for the info.

 

[mickey megabyte]

what exactly is AHCI? (and is it pronounced 'achey' or 'arsey'? )

wikipedia says:

The Advanced Host Controller Interface (AHCI) is a host controller interface defined by Intel which defines the operation of Serial ATA (SATA) host bus adapters in a non-implementation-specific manner.

non-implementation specific?

 

[mendopaul]

I changed mine with the os installed using this tutorial

http://www.sevenforums.com/tutorials/61869-ahci-enable-windows-7-vista.html

That tutorial really did the trick.......many thanks to all who suggested and commented. I gained a lot of good info from you all and increased my confidence in doing this. It seems faster now than before but the machine is so new and and un-loaded that it's not a good time to judge. Actually it was quite simple to do with that tutorial that was very good. I'm a happy camper thanks to all of you!

 

[sandeep108]

Enabling AHCI also enables NCQ. I have generally always found AHCI to be faster, though some people feel it is unstable. I have had no problems with it at all, either with HDD or SSD. With SSD, I believe it really increases performance.

 

[James Colbert]

If I might beat the 'hot swap' drum one more time...a few years ago, I bought about 3 of these front-sata panels:

Akasa Thermal Solution

Then, they were around $12 each and come complete with data & power panel inserts and cables. It fits in a 3 1/2" floppy bay. I got mine from Sidewinder. The above link is to the manufacturer's site. Ignore the term 'Thermal'.

Not for everyone, but I have found these to be very useful.

Where to buy:

http://www.akasa.com.tw/update.php?tpl=wheretobuy.tpl

James

 

[Bill2]

Performance benefits from NCQ happen only with long command queues which are unlikely on a desktop, or if one is running very disk intensive operations. It is of no use to the average home user.

 

[pparks1]

I don't think I have ever tried to pronounce AHCI....instead I simply spell it A H C I. It's the same as IDE, I always spell it.....i never side the word ("ide").

 

[James Colbert]

I don't think I have ever tried to pronounce AHCI....instead I simply spell it A H C I. It's the same as IDE, I always spell it.....i never side the word ("ide").

Perhaps we should set precendent. I vote for the southern pronunciation. If I were to use it in a sentence:

" 'Ah see' it may rain today..."

 

[sandeep108]

Performance benefits from NCQ happen only with long command queues which are unlikely on a desktop, or if one is running very disk intensive operations. It is of no use to the average home user.

That is technically correct. But when using a HDD with ncq I have felt it faster than using a non-ncq HDD. In case of SSD, I am not too sure whether the performance benefit is because of ncq or ahci.

 

[fseal]

I had an occasional lockup problem with NCQ on my Gen 1 SSD and turned it off and benchmarks showed the performance actually went UP a bit with it off. (and the lockups stopped too).

But the difference wasn't enough to actually notice when using it.

Since upgraded my MB and drivers and the NCQ problem is gone and have left it on these days.

 

[sandeep108]

A lot of the performance is also due to the drivers/chipset. e.g. AHCI it seems works best on Intel ICHR 8 and above with their drivers. It does not seem to matter as much with nVidia chipsets, jmicron controllers, etc.