USB device caused POST issues

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This one took me by surprise. I had a Dell Optiplex that refused to get past the POST for about 29 out of 30 times. It would simply run through the POST until about 3/4 of the way and then stop and lock up, forcing you to hold the power button down until it powered off. Repeat 20 to 30 times and you might get lucky enough to see the POST complete and you have a working system.

This wouldn’t be too bad if the machine was never turned off but in these times of crappy weather, limited UPS time and of course in the interests of the environment, it wasn’t really an option.

I ran through all the tests, replaced RAM, optical drives, swapped PSU’s, unplugged everything that was non essential, etc and nothing changed the POST problem. Eventually I got the motherboard replaced along with and new RAM. Still no dice.

Finally I unplugged the KVM switch that was being used and hey presto it booted consistently with no POST problem. It turns out that the  USB part of the KVM switch was causing the machine to freeze during POST. I have never seen this before which was why I hadn’t really played around with it. I seem to have a penchant for thinking that the problems are far more complex than often they are. Why oh why can’t I remember Ockham’s razor…

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One Response to “USB device caused POST issues”

  1. Mat Says:

    My desktop will not boot if me ipod is plugged in. very odd .
    Think you need a new brand of razor lol

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