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  1. #1
    ROG Enthusiast Array
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    Aug 2014
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    Motherboard takes 3-4 X to post and chokes on connected devices

    Hi,

    Got an Asus Z270-WS and depending on which setting in bios is set one way or the other the system will take three - four attempts to post and load windows. I discovered that this is related to the PCIEX4 X2/X4 setting under onboard devices in bios. If set to X4 the system will boot right into Windows no issues. However the downside to that is all of a sudden I noticed that I have a usb port that has failed enumeration and can not start. If I set PCIEX4 to X2 operation that turns on my front panel USB 3.1 controller and that unrecognized failed usb device goes away but it will take like 3-4 attempts to start up cold. Warm boots start up fast. So as far as I'm concerned this is either a defective chip on my motherboard causing this or a flaw with the bios and how it manages resources. Should note I have dual M.2 raid enabled and a U.2 device on U.2_2 and a PCIE NVME drive on the PCIEX4 slot. Frustrating. Whats the point of having a workstation class motherboard if it chokes on all your devices. Anyone experience this and have any suggestions?


    Thanks.

  2. #2
    ROG Enthusiast Array
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    Aug 2014
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    Sucky pcie bus enumeration

    Well yesterday I cleared my CMOS and started over. Wanted to rule out what ever was the cause of the triple post boot behavior. I can definitely say that it is because of the 2X PCIEX4 slot setting under onboard devices section of bios. I think I was able to get rid of the mystery failed enumeration usb device by turning off Fast Boot in Windows and doing the same in BIOS shutting off Fast boot. This probably allows the motherboard and windows to correctly enumerate all of its devices. May have added 1 second to the boot time but I don't care. Set my PCIEX4 slot to use 4X speed effectively shutting of front panel USB 3.1 controller but at least the system doesn't take 3-4 attempts to start up!

    Thanks

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