Computer Bewilderment

[MacolmParticipant @macolm]

Here is a puzzling computer episode. I have a five year old PC running Windows 10. It has a M.2 SSD for the operating system only, a SATA HDD for main data storage and a second SATA HDD used as part of a backup scheme. There is also a DVD writer, and a memory card reader utilising USB3. The problem started when the card reader failed to recognise a camera SD card.

Thinking this might be due to poor contact, I removed the card reader, which looked in good order apart from some dust. I cleaned the various sockets with switch cleaner, and put it back. But switching on, the PC hung, and my heart sank when the blue screen "Attempting Automatic Repair” appeared. I have had little success with Windows repair! However, there was no hard drive activity whatsoever, and after a few minutes it needed a forced switch off. Retrying, the BIOS setup did not reveal anything, indeed all voltages were in spec and all drives shown as present, but the failure to start remained.

An intermittent short circuit or similar hardware fault seemed possible so I proceeded cautiously, disconnecting the card reader, but still the hang. I then disconnected all the SATA drives, and now the PC operated normally with the M.2 drive, with system file checker not indicating any damage.

Replacing the SATA drives one by one, both HDDs operated normally. Reconnecting the DVD writer caused the boot failure, but disconnecting the power cable with the data wire still connected, the fault was gone. The DVD writer was removed, inspected for shorts or damage and powered up from a spare supply with no suggestion of fault. Replacing it with only the power cable connected, the PC worked.

Had that SATA channel failed or been damaged? With some trepidation I transferred the SATA cable to the second HDD, and the fault returned. Back to the original connection, but with a new SATA data cable to the DVD writer, and all was well. A faulty data cable! Yet checking the cable for shorts and continuity, no fault was found.

It is surprising that a SATA malfunction on a secondary channel could hang the whole PC. Certainly the DVD writer is first in boot order, but the second non bootable HDD showed the same malfunction.

One further Windows irritation. The card reader did not initially show up in Explorer, then I remembered that this happens if no drive letter is assigned – I had initiated reinstall. Catch 22! You need a non M$ utility to give the drive a letter. All was then well.

[MacolmParticipant @macolm]

[old martParticipant @oldmart]

I f you have any choice of sata connections on the motherboard, you should try another and make a note of the suspect one. It also helps to be able to try different sata cables.

[Gordon Smith 1Participant @gordonsmith1]

On some motherboards use of a M2 ssd disables some of the Sata channels.

[An OtherParticipant @another21905]

Gordon beat me to it – my motherboard has 6 SATA channels, but channels 5 & 6 are not available if I use an M2 SSD, so you need to check which channels are in use – this was detailed in the handbook provided with the computer.

[MacolmParticipant @macolm]

Thanks for the inputs, and indeed an M.2 drive does disable a particular SATA connection.

The puzzle to me is that while all the SATA ports proved to be working properly, the use of a defective cable on one port prevented the computer from being able to boot into Windows via a different port.

[John Doe 2Participant @johndoe2]

One thing that might be a possibility is the computer power supply failing.

Some supplies are only just sufficient to provide the total current required by all the various devices, and as they age, they can reduce their output, and hence devices start failing. And/or if additional drives have been added, the PSU might not quite be coping; so when a drive attempts to spin up, it could drag the PSU voltage rail(s) down, and the computer might see this and assume a fault with that drive.

When you connected just the power lead to the DVD drive, the computer was OK probably because, without the data lead, the drive was not instructed to spin, so the current drawn was less than it would draw in normal use.

Another possibility is that although you checked the data wires for continuity and shorts, I am guessing you only did this with a DC multimeter? Of course, data wires now work at many megaHertz, and at these frequencies, certain electronic effects can prevent the data being 'cleanly' transmitted along them; for example capacitance between adjacent data cables – which would not show up with a normal multimeter.

Without sophisticated test gear, you are restricted to substituting cables and cleaning connections, as you have been doing.

I would (remove the wall plug), and go over the whole computer internally with a vacuum and a soft brush (very gently), to get any dust out of all the boards and open up the PSU to do the same. Dust can cause overheating and reduced current flow, (and in some cases, short circuits on circuit boards). I would also clean all the connections to the PSU and remake them a few times.

If you remove any items from the computer to clean them, make sure you wear an earthed earthing bracelet around your wrist before handling them – static build-up can kill some components.

Good luck !

[MacolmParticipant @macolm]

Thank you for your suggestions. I am pretty confident of the adequacy of the hardware – that is unless there is a failure. Having replaced the defective SATA cable, the computer has operated properly since.

When that cable was faulty, the BIOS POST (power on self test) did appear to be successful as indicated by a short beep, and which presumably included test of the SATA interface. But thereafter there was no data communication with the Windows SSD or for that matter any other drive as indicated by a complete absence of any HDD LED activity. I suppose it could be due to a coding error in this particular BIOS version. Certainly the boot sector was not damaged, since start up was immediate with the new cable.

[Adam StevensonParticipant @adamstevenson91624]

Try the boot order, A new USB can over ride the old order, even if it is an old device in a new port. I have a disabled the UEFI updating the boot order but the first is a USB3 Memory Drive plugged into Port 2 which is only plugged in if I need the computer to recover via a offline OS on the stick.

[MacolmParticipant @macolm]

Windows seems to be able to change the boot order in the UEFI BIOS and I have previously had problems with that, but in this case boot order remained as previously set up. The DVD is highest to allow for potential disaster recovery, but the problem stayed the same when the faulty cable was moved to a non bootable drive. I don’t seem to have an option to stop boot order being changed or I would have it set.

Of late, Windows updates are a cause of many problems, often due to defaults being restored such as back to “auto”, followed by loosing a carefully set up workaround.

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