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What should I do when Ubuntu freezes?

tl;dr - I have 4 devices sharing 1 IRQ. Is this bad and how do I tell the BIOS to stop it?


I have an old Dell GX280 dual Pentium 4 that I (semi) resurrected last weekend with an installation of Ubuntu 12.04. Everything was going fine the first several hours until a problem that plagued me when WinXP was on that machine happened -- it froze. Completely froze. None of the myriad of ways I have found here on askubuntu helped me to regain control except a long-press of the power button to shut it off. Clearly, this wasn't a software/WinXP issue.

After much googling, I found that hardware conflicts can often cause this sort of total lock-up and with all the odd blocks of yellow and flecks of color showing on my screen (both WinXP and Ubuntu) I figured my old GeForce 7600 was failing and causing me these odd issues. (A good canned-air dusting of the entire interior fixed the color fleck problem)

Again, through much googling and numerous answers found on askubuntu, I somehow stumbled my way onto the lshw command. After going through it, line by line, I found that I have four devices sharing IRQ 16: eth0, wlan0, ide0 (DVD-RW), and my video card. In hindsight, I can recall weird instances of my Ethernet connection to another computer not working when I thought it should. I never full troubleshot those issues so it could be a coincidence.

The other thing that has been plaguing me since installing Ubuntu (wasn't there during WinXP) has been periodic moments of my monitor getting no signal from Ubuntu during boot. The first couple days, it would disappear after the Dell boot screen and reappear at Ubuntu login. Now, it disappears after the Dell boot screen and doesn't return at all -- I have to hit F12 where I can load a safe mode version of Ubuntu and get more details like dmesg and lsdev. I also ran memtest86 overnight and woke up to zero errors, so failing RAM is out.

Where do I go from here?

Update, 3 Sept

So, the below measures did not work. The machine still froze up some time Saturday morning, so I completely excised the video card from the system and plugged the monitor into the good old onboard VGA port. It's been 2 and a half days with no freezes. No big deal, not having the 3D card, I suppose. I wasn't planning on gaming with Ubuntu, anyway. Thanks for all the help and my apologies for posting on the wrong board. Also, I'm not sure how to "reclaim" my original questioned account, so I can't mark the question as resolved.

Thank you, ImaginaryRobots and Steve Kroon.

I went back to the BIOS screen and expanded every single menu, but could find nowhere to edit IRQ settings. IRQ was mentioned only twice as info about a particular device (I don't remember which) but was not a writable piece of information.

While I was in the BIOS settings, I did tell it to use the onboard video controller(?) instead of the one on my GeForce card. I expected to have to plug the monitor into the VGA port, instead of the DVI one on the video card (w/adapter), but the machine booted normally without a plug change, which I still find odd.

As of this morning, it has been about 10 hours with no freeze-up. I will wait out the weekend to see if it behaves itself and come back later to report.

Thank you for the link, Steve. The panic surrounding my shared IRQs has been dispelled and my focus is back on the video card.

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marked as duplicate by Jorge Castro, Eliah Kagan, Mitch, fossfreedom Sep 4 '12 at 11:28

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

This is hardware-related and possibly off-topic, and you can get more help at SuperUser, which specializes in hardware, as well as software for all major OSs. I would bring up another(separate) question about the no signal issue with the monitor at boot, here at Ask Ubuntu. –  hexafraction Aug 30 '12 at 23:03
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2 Answers 2

You likely need to fix the IRQ assignments in your BIOS settings. If at all possible, set it to "automatic", since you shouldn't have to manually set them on hardware made this millenium.

Here's a screenshot from a different Dell machine:


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I must have missed this page/settings in the BIOS screen somewhere. I will look closer in a couple hours when I've gotten home from work and post back here. –  sanpatricio Aug 30 '12 at 21:40
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Shared IRQs are by no means unusual. Sometimes it can cause problems, but it is fairly standard practice nowadays for multiple devices to share a single IRQ. (For example, see the section "Shared IRQ’s – a typical PC solution" at http://karbosguide.com/books/pcarchitecture/chapter40.htm .

So this might be your problem, but just because there are devices sharing an IRQ does not mean there is a problem.

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