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07 Dec 2009  

Microsoft Community Contributor Award Recipient

Windows 7 Home Premium SP1, 64-bit


Thanks for the links. They confirmed my 3 year old opinion. Here are the pertinent pastes from the links provided by Greg and bobkn:

If anything, in your usage scenario, you are likely to see a slight performance decrease as a result of engaging AHCI mode.

The key reason for this is that the native command queueing, assuming your drives are capable of it, fractionally increases latency, which only tends to be outweighed by the benefits of queueing in a usage scenario where there genuinely are loads of concurrent read/write requests being made.

This usually means a server of some sort. Even "power" desktop and workstation users are unlikely to be pushing the queue depths fast enough.

In most home/power/office user scenarios, the performance benefit of disabling NCQ tends to outweigh the demerit of the slower interface, hence IDE being the quicker of the two modes in the real world - and that's forgetting about the boot delay the AHCI BIOS causes.

Is there any advantage to using the AHCI controllers over the IDE Enhanced option on the Sata ports? I ran HD Tach on the drive before I switched from AHCI to IDE. I got a very small performance boost using it in IDE Enhanced mode instead of AHCI. It wasn't much, but a gain none the less.

So, is there any advantage with AHCI over IDE?

you are far better off in IDE enhanced mode which means SATA mode ............ ACHI doesnt shine unless you are running a raid array and even then raid doesnt really give much benefit at all until you get into 3 & 4 drives

From thread that BobKn referred to:

I went back and forth between AHCI being on and being off on my new box that I built in July. Honestly, with almost ever task I did and with any benchmarking tool, I didn't see any real performance gain with AHCI enabled.

Unfortuantely, with AHCI on, I do have about an 8 second delay on each boot as the storage controller initializes. And since I do boot daily, and it was costing me 8 seconds which I didn't pick back up elsewhere, I just run with AHCI disabled.

You have to use I/O bound tasks --otherwise it won't make a huge amount of difference unless you have RAID as well.

However with LARGE photoshop files and > 1 TB size disks the I/O throughput is significantly faster than with the IDE interface - and don't forget before SSD gets cheap enough for us mere mortals to use SATA-2 will be upon us.
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