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Thread: AHCI Mode

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    AHCI Mode

    Just wondering if anyone has seen similar, as it's driving me nuts!!

    Have a self built PC with 2 X 128 GB OCZ SSDs and 2 x 2TB WD RE4 physical HDDs. I have tried 4-5 times over the last couple of years to get this to run successfully in AHCI mode without success. I have tried during a clean install of Win 7 x64 and using the registry change after installing in IDE mode, but the same thing will always happen.

    Everything will be fine in AHCI mode for up to a day, then one of the physical HDDs will drop down into Multi-Word DMA 2 mode (from UDMA 5) and hence any access of that drive is really slow. In IDE mode I never have any problem with the drive, it never drops out of UDMA 5.

    I have checked the properties of the HDD controllers in Device Manager, and some times the 'Enable DMA' check box has been greyed out and hence can't change it, other times it is available but checking it is ignored as it is unchecked again after a reboot.

    This happens with both the MS Win 7 drivers and Gigabyte's Raid/AHCI drivers (have a GA-X58A-UD7 Rev 2 (FD BIOS) mobo - all 4 drives are connected to the Intel ICH10R controller as standalone drives (i.e. no Raid)).

    Would really like to find a resolution, as in AHCI the SSDs are noticeably faster as they run in UDMA 6 rather than UDMA 5 in IDE mode.

    Any suggestions would be greatly appreciated.
    Last edited by Moose48; 2014-01-19 at 01:28.

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    I suspect you have a faulty disk controller / motherboard. You could buy a new disk controller to test, should cost about 20.

    cheers, Paul

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    Hi, Moose.

    DMA dropping indicates a repeating error: http://winhlp.com/node/10 Yes, it's an old article but it does also apply to SATA drives and it contains a number of possible fixes.

    You could try rolling back (or 'force' installing) to the standard MS SATA controller drivers via Device Manager if the drives connected all pass chkdsk and the makers' deep diagnostics. This enables TRIM and often improves SSD performance.

    Recent RE4's appear to be returned more frequently than previously: http://www.hardware.fr/articles/911-6/disques-durs.html

    (There's good reason that OCZ are no longer in business, perhaps you should consider replacing the SSDs with a better brand? http://www.hardware.fr/articles/911-7/ssd.html)

    The above article in French is from a 9 part series, the earlier versions, which might be more pertinent to your specific hardware, were also published in English, the last of those is here: http://www.behardware.com/articles/8...s-rates-7.html

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    Thanks for the responses guys :

    Paul : I do suspect the disk controller, but on the RE4 drive rather than the mobo.

    satrow : Couple of things here dude :

    I don't have any problems with the SSDs in either IDE or AHCI, they appear to work fine in either mode. Although there appears to be conflicting info. many say SSDs perform better in AHCI (i.e. faster) - and this certainly appears to be true in my case, they do benchmark noticeably faster in AHCI (even MS's Experience Index is higher in this mode).

    Wasn't aware of OCZs bankruptcy, but as above, don't have any problem with these drives - they work fine in either mode, and am generally happy with their performance (considering they're knocking on a bit now - Gen 2, Vertex 2 drives).

    Surprised about the return stats on RE4s, especially as you're paying a premium for Enterprise level drives - have bought RE drives for years and have found them very reliable (may have to rethink this now!)

    Was aware of a registry setting to re-enable DMA mode on a drive, but not sure this is a good idea - it's dropping out for a reason, and continually trying to force it back into that mode may cause more problems than it solves.

    Again, thank you for the responses guys, am tempted to think that as the problem is only on 1 RE4 drive and only in one mode (AHCI) it may be the controller on the drive itself - may have to try replacing it when funds allow.
    Last edited by Moose48; 2014-01-19 at 20:04.

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    Just as an update guys, I'm hopeful I may have resolved the issue - touch wood (NO! not that kind ;O) )

    I have left the 2 SSDs on the Intel ICH10R controller and set this to AHCI, then moved the 2 WD RE4s to the GSATA2 controller and set this to IDE.
    Now all 4 drives pick-up in UDMA 6 (the SSDs have always picked-up in UDMA 6 in AHCI, the RE4s have never previously picked-up in UDMA 6 - how strange is that!).
    After the better part of a day, the previously problematic RE4 hasn't dropped out of UDMA 6 - so with any luck! problem solved.

    Thanks again for your input
    Last edited by Moose48; 2014-01-20 at 23:49.

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    Maybe mixing disks with different SATA versions on the same controller caused an issue and the controller dropped back to basic mode. What is the SATA version of the different disks - 1, 2, 3?

    cheers, Paul

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    Hi Paul, all 4 drives are SATA 2 and all 4 were originally on one controller, yet the problem affected only one RE4 HDD.

    It's been 3 days now since I changed to the configuration noted above, and all is still well.

    Have to say I'm at a loss to understand why the problem occurred on 1 drive in the original configuration, and why splitting the drives across 2 controllers appears to have resolved it - also why the RE4s now pick-up in UDMA 6 when they previously only ever went to UDMA 5.

    The only thing that does spring to mind, is that under the original configuration, 2 disks used to appear on 1 ATA Channel under IDE ATA/ATAPI controllers, whereas now, all 4 appear on separate Channels - don't know if this had any influence - but couldn't really identify which was which from the Channel properties.

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    Maybe one has a timing issue in firmware that didn't play well with the controller. A firmware upgrade may fix it, but your solution is easiest.

    cheers, Paul

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    This may be slightly off-topic. Regarding performance when using AHCI vs. IDE mode, in practice it's difficult to tell the difference. Yes, your drives will certainly benchmark faster, but it makes very little difference to the normal functions of a home computer when using an SSD as your boot drive. This is largely because the 2 principal performance advantages of an SSD, namely low latency and small file Read/Write speeds, are still working well even in IDE mode. Having AHCI mode working is, of course, most desirable, but your computer should still feel quick & snappy even in IDE mode. Anyway, glad to hear you resolved the issue of one HDD dropping out to lower performance. It would be interesting to know the true explanation of why your solution worked!

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    starvinmarvin : Would totally agree with you - it may be my imagination, but I believe (big) apps. start a tad faster, but really not much in it, if it all. Please see below for possible explanation of problem.

    Paul T: I believe you may have nailed it Sir! Have done a lot more digging, and it appears that certain firmware revisions of the WD2002FYPS RE4 do have firmware timing issues (amongst other things!), especially when drives of different firmware revisions are used together. I bought both my drives from the same vendor at the same time, so would have hoped for/expected the same batch/firmware revision - but no, they're different (and I do have what appears to be the problematic firmware revision).

    Have found numerous complaints of these revisions dropping out of RAID arrays particularly and dropping to a 1/3 of their speed (my problem I would assume).

    Your closing point is also spot on, there is a firmware update to resolve these issues, but as I have a workaround that appears to work, will let sleeping dogs lie.

    Many thanks guys.

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