Sorry in advance for this lengthy post but I am trying to include as much information as possible so that it might help others.
Some background:
I purchased this Dell 7537 laptop recently with the intention of installing Ubuntu 13.10 64 bit in a dual boot mode with Windows 8. I know there's a few hoops to jump through in order to succeed, but I've used Ubuntu for several years now and know what to expect.
This is not what this post is about though. It's to compare notes with anyone who may have encountered a particular problem with this laptop in trying to do the same.
I've already taken steps to return my laptop as it's less than 2 weeks old but would happily change it to a replacement if it can be shown that it's only my laptop that has the problem/fault.
If nothing else, it may be useful to others that follow as I've been unable to find anything about this just by Googling.
The Problem:
I intended to just use the Ubuntu startup USB disk for a week or two to satisfy myself that it all worked as expected before committing to an install. It's when I shut the Ubuntu system down that the laptop would randomly restart again within 5 seconds.
This was not a rare occasion but at it's worst, it would do it every second shutdown. I've done a lot of testing to try to solve the problem and will outline that shortly, but I will add that random restarts also occurred with the installed Windows 8, albeit infrequently. I tried all the fixes I found for preventing Windows from doing that, like turning off WOL and restarts due to system problems at shutdown, but still it did it.
What I have done is a LOT of booting and shutdowns of Ubuntu trying to find the problem and have come to the conclusion that it is some kind of electrical interference, particularly on the USB ports at the left. I do have an electronics background so am fairly confident in saying this. It could be that my motherboard has missed out on some vital filtering components during assembly, or it could be a common problem and therefore a shortcoming in design. Either way, it may not be something that would be noticed under normal circumstances but I have no way to tell.
I will also add that this problem only occurs with the AC adapter plugged in and turned on (we use 240V in this country). It does not occur when on battery power alone, or with the adapter in but turned off.
These are the results I obtained:
The worst affected USB port is the one closest to the AC adapter input on the left hand side.
When booting from there with my power adapter on it would restart once every two shutdowns, on average. The port on the right hand side that I tried had zero restarts out of twenty shutdowns and didn't seem to be affected at all!
When I realised this I immediately suspected the power adapter as being “electrically noisy”, but this is only half the story.
I tried another Dell adapter which was exactly the same as mine but a year older. It still caused random restarts but less than half the number of mine.
I tried an even older HP adapter with similar “less than half” results .
So, while the substitute adapters seem electrically quieter than my adapter, I still got random restarts on the left hand side USB ports.
Incidentally, if anyone gets infrequent random restarts with Windows 8 after trying all the “usual” fixes, it could be a “noisy” adapter causing it. I suspect my Win8 wouldn't restart at all if I changed the adapter for a less noisy one. But that's not solving the whole issue for me.
I also tried using a different USB flash drive as a Ubuntu startup disk but got much the same results as before.
Conclusion:
If someone else is able to try this experiment of booting and shutting down a Ubuntu USB startup disk a number of times from the USB port closest to the power adapter, with it plugged in and turned on, it may help others in the future.
I know that I could boot or install Ubuntu from the non-noisy port on the right hand side, but that's not the issue. It's the long term reliability of using the left hand side ports for anything at all. Could data integrity be compromised on occasions, for example? You might not know till it's too late.
