7 Replies Latest reply on Apr 27, 2011 8:54 AM by cangelim

    System Interrupts causing heavy load on cpu

    cangelim

      Hi,

       

      Spec: Core i5-2500 on a DH67BL (b3) motherboard, 8GB RAM kingston ddr3 and Seagate 1TB SATA  6gb/s

      BIOS: 15-apr-2011

       

      I've just assembled and installed (formatted) win 7 home premium. To my surprise, I had one entire CPU permanentely loaded with system interrupts. Done bios upgrade, all OS' upgrade and always the same results showing. Tried even Ubuntu and CPU 0 kept 100% loaded with system interrupts....

       

      xperf showed the cause was acpi.sys, but so far no changes I've made in the BIOS config could change the result. Does anybody have a tip on this?

       

      Thanks in advance.

      Carlos

       

      Attachment: screenshot of resources monitor (windows is in portuguese)

      process resources.png

        • 1. Re: System Interrupts causing heavy load on cpu
          Flying_Kiwi

          What do the two CPU history panes in Win 7 Task manager, performance tab show? I'm wondering if it's just a software monitoring issue with this new CPU/Hardware...

           

          [Edit: Oops that's 4 history panes for an i5 CPU - one per core (I was thinking of what my Core 2 Duo shows)]

          • 2. Re: System Interrupts causing heavy load on cpu
            cangelim

            Thanks for your interest.

             

            Actually, it was task manager's results that first caught my attention.

             

            I tried to eliminate a possible software monitoring issue by testing the machine with linux. The exactly same results showed on ubuntu 10.10: first cpu (cpu 0) being heavy loaded while the others at a more normal state. As the problem was consitent between two different OS, I got back to win 7.

             

            Here's my Task Manager's screenshot

            taskman.png

            • 3. Re: System Interrupts causing heavy load on cpu
              Flying_Kiwi

              If it's on a totally fresh install with officially supplied drivers direct from the motherboard maker and before installing any additional software (ie your first noticing it in Task Manager was without xperf or any software installed on the 'bare' O/S) then I'd put it down to a hardware error. I found this thread (same problem under Vista 64) at another forum http://www.tankspot.com/showthread.php?69562-Problem-with-ACPI.sys-and-DPCs-Interrupts-causing-pegged-CPU where the owner fixed the same issue with a 'dust off and reassemble'.

               

              If you try that and it still plays up, I'd get in touch with your motherboards tech support dept. Sorry I can't be anymore help but both of my Core 2 Duos cores have behaved themselves in Task Manager all along.

              1 of 1 people found this helpful
              • 4. Re: System Interrupts causing heavy load on cpu
                cangelim

                Thanks a lot!

                 

                I'll try reassembling the beast when I get home and will share any results. Hope they will be good.

                • 5. Re: System Interrupts causing heavy load on cpu
                  cangelim

                  Ok... here's the short version: IT WORKED!!!!!!!!!

                   

                  I've seen weird things before, but this... The cause was a screw!

                   

                  Many thanks to Flying_Kiwi for the link on the forum. As said, I reassembled the machine, but to no avail. After many different attempts, I decided to take the motherboard off from the CPU. When I turned it on without any screws to hold it on the cpu, I was shocked (and delighted) to see that those damned interruptions were no more.

                   

                  Next step: find which were the screws causing the malfunction. With the machine turned on and task manager running, I took the risk to tighten each screw in order to see when the interruptions would occur. I managed to tighten all of them with the exception of this one, which I think fills the "R" hole.

                   

                  Here's task manager's screenshot of three attempts to tighten the son of a gun. Took it out and now I'm happy

                  screwing screw.png

                  • 6. Re: System Interrupts causing heavy load on cpu
                    Flying_Kiwi

                    cangelim wrote:

                     

                    Ok... here's the short version: IT WORKED!!!!!!!!!

                     

                    I've seen weird things before, but this... The cause was a screw!

                    I'm glad you've got it sorted but I would have thought not being able to correctly install a mounting screw would constitute a hardware failure worthy of replacement under warranty (should you choose to go down that path).

                    • 7. Re: System Interrupts causing heavy load on cpu
                      cangelim

                      I thought about that, too. Will talk to my supplier soon. Thanks again for your interest!