I very recently bought a new desktop computer. The motherboard is: Z77MX-D3H and the power supply is ocz zs series 550w. The issue I have is that once I boot to the operating system (I have tried with fedora and Ubuntu with kernels 2.6.38 - 3.4.0), my hard drive (2.5" Magnetic) occasionally makes a power switch noise and it resets. Needless to say, when this drive is the OS drive, the OS crashes. I also have a SSD that works fine with the same OS configurations, but if I have the magnetic hard drive attached as second drive, it works erratically and the reconnects result in corrupted data. I also noticed that whenever I plug an external hard drive USB2.0 or USB3.0 to the computer the issue with the reconnects is even worse: [ 52.198441] sd 7:0:0:0: [sdc] Spinning up disk... [ 57.955811] usb 4-3: USB disconnect, device number 3 [ 58.023687] .ready [ 58.023914] sd 7:0:0:0: [sdc] READ CAPACITY(16) failed [ 58.023919] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.023932] sd 7:0:0:0: [sdc] Sense not available. [ 58.024061] sd 7:0:0:0: [sdc] READ CAPACITY failed [ 58.024063] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.024064] sd 7:0:0:0: [sdc] Sense not available. [ 58.024099] sd 7:0:0:0: [sdc] Write Protect is off [ 58.024101] sd 7:0:0:0: [sdc] Mode Sense: 00 00 00 00 [ 58.024135] sd 7:0:0:0: [sdc] Asking for cache data failed [ 58.024137] sd 7:0:0:0: [sdc] Assuming drive cache: write through [ 58.024400] sd 7:0:0:0: [sdc] READ CAPACITY(16) failed [ 58.024402] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.024405] sd 7:0:0:0: [sdc] Sense not available. [ 58.024448] sd 7:0:0:0: [sdc] READ CAPACITY failed [ 58.024450] sd 7:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 58.024451] sd 7:0:0:0: [sdc] Sense not available. [ 58.024469] sd 7:0:0:0: [sdc] Asking for cache data failed [ 58.024471] sd 7:0:0:0: [sdc] Assuming drive cache: write through [ 58.024472] sd 7:0:0:0: [sdc] Attached SCSI disk [ 58.407725] usb 4-3: new SuperSpeed USB device number 4 using xhci_hcd [ 58.424921] scsi8 : usb-storage 4-3:1.0 [ 59.424185] scsi 8:0:0:0: Direct-Access WD My Passport 0740 1003 PQ: 0 ANSI: 6 [ 59.424406] scsi 8:0:0:1: Enclosure WD SES Device 1003 PQ: 0 ANSI: 6 [ 59.425098] sd 8:0:0:0: Attached scsi generic sg2 type 0 [ 59.425176] ses 8:0:0:1: Attached Enclosure device [ 59.425248] ses 8:0:0:1: Attached scsi generic sg3 type 13 [ 61.845836] sd 8:0:0:0: [sdc] 976707584 512-byte logical blocks: (500 GB/465 GiB) [ 61.845838] sd 8:0:0:0: [sdc] 4096-byte physical blocks [ 61.846336] sd 8:0:0:0: [sdc] Write Protect is off [ 61.846338] sd 8:0:0:0: [sdc] Mode Sense: 47 00 10 08 [ 61.846718] sd 8:0:0:0: [sdc] No Caching mode page present [ 61.846720] sd 8:0:0:0: [sdc] Assuming drive cache: write through [ 61.848105] sd 8:0:0:0: [sdc] No Caching mode page present [ 61.848106] sd 8:0:0:0: [sdc] Assuming drive cache: write through [ 61.857147] sdc: sdc1 [ 61.858915] sd 8:0:0:0: [sdc] No Caching mode page present [ 61.858916] sd 8:0:0:0: [sdc] Assuming drive cache: write through [ 61.858918] sd 8:0:0:0: [sdc] Attached SCSI disk [ 69.875809] usb 4-3: USB disconnect, device number 4 [ 70.275816] usb 4-3: new SuperSpeed USB device number 5 using xhci_hcd [ 70.293063] scsi9 : usb-storage 4-3:1.0 [ 71.292257] scsi 9:0:0:0: Direct-Access WD My Passport 0740 1003 PQ: 0 ANSI: 6 [ 71.292505] scsi 9:0:0:1: Enclosure WD SES Device 1003 PQ: 0 ANSI: 6 [ 71.293527] sd 9:0:0:0: Attached scsi generic sg2 type 0 [ 71.293668] ses 9:0:0:1: Attached Enclosure device [ 71.293758] ses 9:0:0:1: Attached scsi generic sg3 type 13 [ 73.323804] usb 4-3: USB disconnect, device number 5 [ 101.868078] ses 9:0:0:1: Device offlined - not ready after error recovery [ 101.868124] ses 9:0:0:1: Failed to get diagnostic page 0x50000 [ 101.868131] ses 9:0:0:1: Failed to bind enclosure -19 [ 101.868288] sd 9:0:0:0: [sdc] READ CAPACITY(16) failed [ 101.868292] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868296] sd 9:0:0:0: [sdc] Sense not available. [ 101.868428] sd 9:0:0:0: [sdc] READ CAPACITY failed [ 101.868434] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868439] sd 9:0:0:0: [sdc] Sense not available. [ 101.868468] sd 9:0:0:0: [sdc] Write Protect is off [ 101.868473] sd 9:0:0:0: [sdc] Mode Sense: 00 00 00 00 [ 101.868580] sd 9:0:0:0: [sdc] Asking for cache data failed [ 101.868584] sd 9:0:0:0: [sdc] Assuming drive cache: write through [ 101.868845] sd 9:0:0:0: [sdc] READ CAPACITY(16) failed [ 101.868849] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868854] sd 9:0:0:0: [sdc] Sense not available. [ 101.868894] sd 9:0:0:0: [sdc] READ CAPACITY failed [ 101.868898] sd 9:0:0:0: [sdc] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 101.868903] sd 9:0:0:0: [sdc] Sense not available. [ 101.868961] sd 9:0:0:0: [sdc] Asking for cache data failed [ 101.868966] sd 9:0:0:0: [sdc] Assuming drive cache: write through [ 101.868969] sd 9:0:0:0: [sdc] Attached SCSI disk Now, if I plug the same drive to the powered usb 2.0 hub of my monitor, the issue is not reproduced (at least on a 20h long operation). Also the issue of the usb reconnects is less frequent if the hard drive is plugged before I switch on the computer. Does anybody have some advice as to what I could do? Which is the faulty part/s that I should replace? As for me, I really don't know if to point my finger to the PSU or the Motherboard (I have updated to the latest firmware and checked the BIOS settings several times). EDIT: The reconnects are happening both in the Sata connected drives and the USBX connected drives.