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    zBook 17 g2 - poor DPC Latency performance when running from z Turbo Drive PCIe SSD

    Discussion in 'Hardware Components and Aftermarket Upgrades' started by rgames, May 18, 2015.

  1. rgames

    rgames Newbie

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    I'm setting up a new zBook 17 g2 and am getting very poor DPC latency performance (> 6000 us) when running from the PCIe SSD.

    I've re-installed the OS (Win 7 64 bit) on both the PCIe SSD and a SATA HDD and the DPC latency performance is fine when running from the HDD (50 - 100 us) but horrible when running from the PCIe SSD (> 6000 us). I've updated the BIOS and tried every combination of driver and component enabling/disabling I can think of. The DPC latency is extremely high from the initial Windows install with no drivers installed. Adding drivers seems to have no effect on the DPC latency.

    Before purchasing the laptop I found this review:

    http://www.notebookcheck.net/Review-HP-ZBook-17-E9X11AA-ABA-Workstation.106222.0.html

    where the DPC latency measurement (middle of the page) looks OK. Of course, this is the prior version of the laptop and I believe it does not have the PCIe SSD. Combining that with the fact that I get fine performance when running from the HDD I am led to believe that the PCIe SSD is the cause of the problem.

    Has anyone found a solution to this problem? As it stands right now my zBook is not usable for digital audio work when running from the PCIe SSD. But it cost me a lot of money so I'd sure like to use it...!

    Thanks,

    rgames
     
    rgames, May 18, 2015
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  2. TANWare

    TANWare Just This Side of Senile, I think. Super Moderator

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    Sometimes different wireless drivers or the like can cause an issue. Is the DPC latency, booted from SSD in safe mode, still bad?
     
    TANWare, May 18, 2015
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  3. rgames

    rgames Newbie

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    Hi Andy - yes, I've found that wireless drivers can cause significant spikes in DPC latency. While troubleshooting this issue I have disabled the wireless to remove it as a potential problem. But even with it enabled the HDD boot seems to be fine with the wireless adapter running, albeit at slightly higher average latency.

    The thing I'm trying to figure out is why DPC latency is fine when I boot from the HDD and terrible when I boot from the PCIe SSD. I'm using exactly the same drivers for all components (including wireless when enabled) in both instances.

    Thanks,

    rgames
     
    rgames, May 18, 2015
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  4. TANWare

    TANWare Just This Side of Senile, I think. Super Moderator

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    OK so in safe mode you still have the high latency?
     
    TANWare, May 18, 2015
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  5. rgames

    rgames Newbie

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    How can I measure the latency in safe mode? DPCLatencyChecker won't run because the services it uses are disabled.

    Further, the audio apps I'm using won't run because there are no audio drivers running.
     
    rgames, May 19, 2015
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  6. TANWare

    TANWare Just This Side of Senile, I think. Super Moderator

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    My bad, I could have sworn that I had run it before in safe mode. My thought here is the SSD is not the only thing on the PCIe bus. Try this one to see if it helps track the issue.

    http://www.resplendence.com/latencymon
     
    TANWare, May 19, 2015
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  7. alexhawker

    alexhawker Spent Gladiator

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    Have you tried both legacy and UEFI installs?
     
    alexhawker, May 20, 2015
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  8. rgames

    rgames Newbie

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    Hi Alex - thanks for the tip. I tried changing the BIOS type but, alas, it did not affect the performance. It was booting in Legacy mode but I switched to UEFI mode and booted into Win 8.1 and the problem remained.

    Thanks,

    rgames
     
    rgames, May 21, 2015
    #8