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In my 20 years of working with computers, I've always assumed that the hardware reset button on a desktop machine was hard-wired to the motherboard, causing some kind of short-circuit which would reset the machine no matter what state it was in (except for power off of course).

I was completely surprised to learn that on my current Core i5-2500 machine, with an ASRock H67M-GE motherboard, this doesn't seem to be the case, at least not when running Ubuntu.

Instead of resetting immediately, the reset button now does nothing when pressed shortly. When pressing it for a few seconds, the machine shuts down instead, to a somewhat mysterious state (it's not the 'normal' shutdown state, I'll see if I can elaborate on that later).

When running Windows, the reset switch works as expected. Also, the reset switch works fine when I'm in the BIOS / EFI. As soon as any Ubuntu component has been loaded (it starts from the moment I see the startup menu from the Live CD), the reset button stops working normally.

Can anyone explain to me how such a thing is even possible? Has the reset button 'wiring' perhaps been changed since the introduction of EFI? And could this be described as a bug in Ubuntu?

I'm running Oneiric since earlier versions of Ubuntu wouldn't even start from the live CD. Not even MemTest (!!) would work properly. Again, Windows booted just fine, no matter the version. I must admit I didn't try installing from the Alternate CD, but IMHO that shouldn't be necessary on a 'normal' desktop PC. And it also shouldn't be related to the reset button problem :-)

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closed as off topic by Bruno Pereira Mar 13 '12 at 16:11

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AFAIK there are some issues with Ubuntu and EFI. The live CD should work normally if you remove the folder "EFI" before burning it onto a CD. Additionaly, modern motherboards sometimes allow you to change the meaning of the reset button in the BIOS configuration. –  FUZxxl Oct 7 '11 at 12:15
    
There must be limitations when running an OS from a CD drive compared to running it from an install on the machine, don't you think? Could this be the reason for this so-called bug of yours. Why are you pressing Reset during the loading phrase of an OS running from a CD drive? IMHO I am a lot of money short of calling an Intel Core i5-2500 an 'normal' desktop machine. –  grahammechanical Oct 7 '11 at 13:14
    
@FUZxxl - right... I didn't know that. I could not find anything related to the reset button in the BIOS, so I never thought that would be possible. I'll try removing the EFI folder before burning the Ubuntu CD to see if that fixes anything. –  Matthijs Oct 7 '11 at 14:16
    
@grahammechanical - why would I press reset during the loading phase of an OS? Well if the machine just freezes, there aren't a lot of other options don't you think? And as for the i5-2500, it's not like that's "state of the art" or a very rare CPU. Why can Windows 7 (dating from oktober 2009) boot properly while Ubuntu 9.10, 10.04, 10.10 and 11.04 cannot? –  Matthijs Oct 7 '11 at 14:16
    
@Matthijs The reason is probably documentation. Sometimes it's very difficult for a Linux hacker to get the required documentation and apply the knowledge, as they have to sign NDAs that prohibit documenting or using such things in FLOSS code. –  FUZxxl Oct 7 '11 at 14:26

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