General discussion

Devices connected to PC randomly getting disconnected

Aug 19, 2018 1:27AM PDT

I seem to have a strange issue with my PC. The devices which are connected to it are randomly getting disconnected, only to be connected again in like a second.

I typically observe the issue when I connect a usb 3.0 drive to the pc and start copying large ammounts of data (direction of data transfer does not matter).
When the copying happens I look at the transfer speeds to/from the usb drive and see that it hovers about 70MB/s then drops to 0MB/s every few seconds.

During those periods when I observe 0MB/s copying speed, sometimes this usb drive disappears from the system only to be reconnected in a second. Sometimes I also see my keyboard and mouse lose power and disconnect also. Even bluetooth mouse sometimes get disconnected during this period (it reconnects in a few seconds, but I cannot move mouse during this periods).

Another issue which happens pretty randomly is when I reboot I see that one of my harddrives is missing (I can sometimes see it as not formatted properly), but when I reboot again the drive reappears. I think this was caused by faulty hard drive, but I've already replaced all of them during few months and the issue is still here.
I've also noticed that hard drive is disappearing more frequently if I connect additional sata hard drive to the PC.

I'm starting to think this is either a faulty motherboard or a psu (will try replacing the psu first).
I'm asking here, because maybe someone had a similar problem and could point out a possibly faulty component which could cause this, or point out what else could I try.

What was done:
Check disk was run on all drives (there were sometimes errors caused by sudden disconnect of a drive, but were repaired, when run again there were no errors).
Hard drives which were thought to be faulty were replaced.
Computer was cleaned inside.

Computer specification:
Cpu: Intel Core i5 6600k @3.5 (stock speed, not overclocked),
Ram: Corsair DDR4 2x4GB 2400MHz, CL14, Vengeance
Mobo: Gigabyte GA-Z170-D3H rev. 1.0 (bios F5)
PSU: CoreXStream OCZ-CXS500W
Drive 1 (system): Samsung 850Evo 250GB
Drive 2: Hitachi 2TB (HUA723020ALA641)
Drive 3: Seagate 250GB (ST3250620NS)
Usb hard drive: Seagate expansion 1.5TB - when copying to/from this drive the errors happen more frequently, but the drive itself is perfectly stable on another pc
Hub: Chinese usb 3.0 hub (problem happens with this disconnected as well)
Keyboard: Genesis R33 usb
Mouse: A4tech XL-747H usb

Is there anything I can do to narrow down which component is faulty?
Best regards and thanks in advance

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Try the usual as well.
Aug 19, 2018 7:17AM PDT

1. Be sure the BIOS is current.
2. The PSU is Dual +12V Rail so these tend to have issues when folk add a GPU. Good idea to swap that first for a new slightly bigger capacity Single +12V Rail model.
4. TEST on USB 2.0 ports.
5. Power delivery over USB can be iffy on some PCs. Get and test with the usual USB Y cable (doubles up the power available.)
6. Ask the PC maker which set of machine drivers to use. Microsoft will not always get this right.

Run a Speccy report and be sure values 01 and 07 are not reporting high values. If you want others to read this for you, read

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Speccy report
Aug 19, 2018 9:57AM PDT
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Look at the drive SMART values.
Aug 19, 2018 10:25AM PDT

S.M.A.R.T attributes
Attribute name: Read Error Rate
Real value: 0
Current: 101
Worst: 76
Threshold: 6
Raw Value: 00071526B8
Status: Good

That's a typical finding and not a drive I'd keep around. While the status is "Good" you always find the owner complaining about issues in copying or use of these drives. It can also show up as nearly explainable (until you know what to look for) pauses and more in Windows.

To see what a good drive looks like, compare those 01 and 07 values to your Samsung and Hitachi drives.

Was the USB HDD unplugged during the run? I didn't see it so no report on its health.

-> I see you have a Nvidia 650. So let's find it's Watts (TDP.) It's 65 so I'll give the PSU a passing grade for now unless the PSU is 4 or more years old. The lower of the two +12V supplies is 20A or 240W. To see if we are pushing it too hard we take the TDP of the GPU, CPU, 20W per drive (regardless of SSD or HDD) and see where we land.

65 (GPU) 91 (CPU) (60W for 3 drives) and let's just call it 216W which is getting too close to the 20A 240W +12V rail. Give that PSU a few years of aging and it's suspect.

There's a lot of IP connections by System so I'd turn the following off (unrelated to your top issues.)

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Usb drive
Aug 19, 2018 11:07AM PDT

Hi, yes you're right the usb drive was disconnected during this run.
I've connected it again to usb 3.0 located on the back (was using a front usb 3.0 when I observed the problem).
Here is the result:

When I look at smart parameter, which value should I look at? I mean there are two values for each parameter labeled 'current' and 'real value' which one is relevant?

I'm a little affraid to try updating the bios, one of my previous mobos died during such operation, would prefer to skip this unless absolutely necessary. Hope you don't mind Happy

The PSU is 5 years old minimum (probably closer to 6, I would have to find order details to know exactly), so I will try replacing that.
I'm thinking about this one:
How do I know if it's single line psu? Do you know if it is a good psu? This is just a first look I will read more to find a proper psu.

I will try to order a new psu tomorrow and I'll go to a local shop for the usb y cable (they're closed today).

I will rerun the copying with usb 3.0 rear ports and usb 2.0 front and rear ports and I'll post back a result.

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You can look at real and current.
Aug 19, 2018 11:17AM PDT

There are many web pages on reading those values but it's very clear as we compare your 200GB Seagate to the others that it's in trouble.

Let me be clear I do not debate this area. It's very well done and when I find a failing drive, I note it and move on. There are folk that want me to write at length each time this is found. Sorry but I defer to the past, the web and don't want to spend time repeating what's out there. It's dead Jim. (well, not dead, but getting there.)

The Seagate Expansion SCSI Disk Device smart values look OK.

-> About the front USB ports. So far these are always trouble. I don't use them and avoid all the hassles that come with them. Test if you want, but I wouldn't bother.

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Failing drive
Aug 19, 2018 11:24AM PDT

Thanks for all your help I'll get the data out of the failing drive and disconnect it. I'll then retest again.

For now I've disconnected the faulty hard drive and run tests again.
The issue appears when usb drive is connected to usb 3.0 on the back panel but it doesn't seem to happen when I connect it to usb 2.0 port.

I'm not fully convinced this is only usb 3.0 which is failing because all this time both usb keyboard and usb mouse are connected to usb 2.0 ports on the back panel and when file copying triggers the issue they lose power and diconnect.

I'll search for the new PSU and retest with it. If the issue will continue I will try replacing the motherboard, since I'm out of ideas.

Again thank you very much for all the help.

Post was last edited on August 19, 2018 11:49 AM PDT

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Since it works elsewhere
Aug 19, 2018 12:40PM PDT
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Usb Y
Aug 19, 2018 12:43PM PDT

I will try to pick this up at local shop and post back the results.

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Drive problem
Aug 29, 2018 11:14AM PDT

Post was last edited on August 29, 2018 11:44 AM PDT

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Aug 22, 2018 4:17PM PDT

We would also like to recommend you to exchange the drive.

Is it still under warranty?

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Aug 29, 2018 11:11AM PDT

Hi, do you mean the internal 250GB drive, that is showing signs of failure, or external usb 3.0 drive I'm using?

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In addition to
Aug 19, 2018 4:54PM PDT

And nothing to do with the usb drop out and your hdd being junk.

You have the ram in the wrong slots.

Your running single channel so look in your manual for the proper slots for the ram.

All of your disk are running a little warm so keep that in mind.

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Dual channel
Aug 29, 2018 11:15AM PDT

Hi, thanks for this information, you were right.
I switched the ram to proper slots.

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Aug 22, 2018 3:10PM PDT


check the drives with the diagnostic software of the manufacturer, which is in this case SeaTools for Windows. This is the manual for that software. Happy

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Aug 29, 2018 11:17AM PDT

Hi thanks for the information I will check usb drive with this since after PSU change I suspect it might be the second point of failure.

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Dec 1, 2018 2:04AM PST

I think it is fixed now. I took the risk and updated the bios from F5 to F22f and I didn't see this problem ever since.
I'm running it for 3 weeks now. I'm posting this just in case someone else will have the same problem in the future.

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I find BIOS updates to be zero risk.
Dec 1, 2018 8:14AM PST

I lost count years ago how often I update. My rule is to not update unless it's in for issues like yours.

I see my first reply was "1. Be sure the BIOS is current" along with you checking the HDD Smart values 01 and 07 which just a few days ago I had another personal experience with.

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