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Best way to disable NCQ?


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#1 stoff

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Posted 01 November 2006 - 07:50 AM

Hi everybody.

I'm not sure which approach is best to disable NCQ on my new Raptor when I'm going to built a brand new system.

One option is to just make sure that AHCI is disabled in the bios (on the Asus P5B Deluxe) and set it to IDE before installing Windows XP. But there may also be an option to set it later in the drivers, if I go with AHCI. Does anybody know what is recommended? Any negatives from disabling AHCI?

#2 RK

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Posted 01 November 2006 - 09:51 AM

Hi everybody.

I'm not sure which approach is best to disable NCQ on my new Raptor when I'm going to built a brand new system.

One option is to just make sure that AHCI is disabled in the bios (on the Asus P5B Deluxe) and set it to IDE before installing Windows XP. But there may also be an option to set it later in the drivers, if I go with AHCI. Does anybody know what is recommended? Any negatives from disabling AHCI?


Disabling AHCI will have the effect of making the SATA controller emulate a PATA controller. In practice this means that SATA-dependent features such as NCQ or hot plugging as well as transfer rates over 132 MB/s will not be possible. Note that, since Windows XP does not support AHCI by itself[1], you will need drivers from the motherboard/chipset manufacturer. In that case, you would press F6 while booting the install CD and use those drivers. Turn AHCI off, and you will use the default ATA drivers in Windows. Although this will prevent transfer rates over 132 MB/s, this should have little effect on you as AFAIK no single HDD available today has a STR high enough that UDMA mode 6 would not be fully sufficient. Higher speeds would at best benefit burst transfers. The real-would performance gain is certainly minimal.

[1] Not 100% sure whether Windows would detect an AHCI controller as a standard IDE controller or a RAID/SCSI controller. In the former case, enabling AHCI without using the appropriate drivers would have no effect, whereas in the latter case XP setup will not allow you to continue.

#3 stoff

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Posted 01 November 2006 - 10:03 AM

Thanks! :)

Do you know whether it is possible to disable TCQ/NCQ in the drivers if one manages to install Win XP with AHCI enabled?

#4 Spod

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Posted 07 November 2006 - 01:37 AM

Do you know whether it is possible to disable TCQ/NCQ in the drivers if one manages to install Win XP with AHCI enabled?

Yes, it's usually possible to disable NCQ (where it's supported) from the drive or controller properties in Device Manager.
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#5 stoff

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Posted 12 November 2006 - 10:05 AM

Yes, it's usually possible to disable NCQ (where it's supported) from the drive or controller properties in Device Manager.


Thanks for the reply, Spod!

So one last question: If performance is the goal, would you recommend to disable AHCI in the bios and letting the OS use the drives as IDE - or would you enable AHCI, letting the OS use them as true sata drivers and then just disable NCQ/TCQ in the driver properties? :)

#6 Spod

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Posted 22 November 2006 - 01:44 PM

Late response, but I'd enable AHCI in the BIOS and tell it not to use NCQ in the driver. You may or may not see any difference, but unless you encounter problems, I'd prefer to enable whatever advanced features are available, even if you don't expect to exploit them fully.
If I'm wrong, please tell me why. I'm trying to help, but I'm here to learn, too.
See my profile for PC specs. I do not practise what I preach.



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