Windows 7: Hardware Interrupts causing 25% - 30% CPU usage

Hi, I recently bought a computer (8 months ago) for my university research and occasional gaming. Its a very fast i7 core based system. I have had no problems whatsover up until last week (Please see system specs)

I recently received a free upgrade to windows 7 because I purchased my pc after june 2009 where you get a special offer from the store. I really like the new OS. Its elegant, fast and looks good. I have had windows 7 for about 1 month. However, just last week I noticed the CPU usage was between 25-30%. Core 3 was completey loaded while others are partially coping. Three are still parked at idle (see attached) . The PC still runs fast but I have noticed slight performance degradation occasionally as the CPU load fluctuates. In addition, whenever I restart the system appears to HANG, after a delay it resumes its normal cycle and the OS starts.

I therefore proceeded to try every trick in the PC book (including hitting the desk!) to try and resolve the problem. This is what I have tried so far as well as the facts to this point. The bold points are the problem areas. Are they related?? I wonder.

• Memory test (OK)
• CPU temp (OK)
• Graphics card temp (OK)
• Drivers (Up to date however the driver scan reports and error on the keyboard and mouse not being fully installed or bad ACPI driver error)
• Ran in safe mode. Problem still there.
• Turned off all unneccessary services and strartup tools. Problem still there.
• ChKDisk (OK but reverts to BSOD driver_power_state_failure, is this related?)
• Ran process explorer to determine the process causing problems (Apparently there is around 10% towards hardware interrupts (see attached diagram)
• In looking at the internals of the 'system' process it appears that a file called ACPI.sys+0x1af44 (see attached diagram) has reared its ugly head and taking 8%.

I also noticed that when powered up cold where I have not used it for a while there is a delay in the Hardware interrupts appearing of approx 1 hour. Now, what I want to know is what the hell is going on with the system and if I have any options left other than performing a full wipe and starting over again (my worst case scenario as I have a lot of custom settings invoked).

Just to let you know I have searched the forum extensively with the topic based on hardware interrupts but as always each mans story is always told a little bit different.

Any suggestions?? I would really appreaciate ANY pieces of advice or ideas on how to get rid of this annoying problem.

Thank you for your time.
Benny

Any takers guys?

Will pay £50 through paypal if anybody can sort this out, its an annoying problem. Just to update when I plugged the computer in and turned the switch at the socket the computer turned on straight away. I get the feeling the signs are pointing more to hardware than drivers.

Hope you can help me.

Did you run the DPC Latency Checker? It may point you to the cause.

Hi, thanks for your reply.

Yes I ran latency checker and everything is in the green. 150 units avg which is nothing. So i guess that rules out the network card. Do you think any of the resart "pauses" point to a PSU overheating?, I have system tools which tells me everything is fine but cannot check the PSU temp. Its a very quiet system but now I can hear the CPU fan intermittently.

Like i mentioned before when the system powers up cold I do not have this problem then after 30 minutes the NT Kernal keeps popping up at first intermittently then it remains fixed and draws CPU usage.

Hmm, the fact that it only starts after a while may suggest a heat problem. Question is where. The PSU is an unlikely candidate unless you overloaded it by adding a high powered Graphics card. Also, the PSU does not generate interrupts and you apparently get an unusual interrupt stack.
I suggest you disconnect everything non-vital including the DSL and run for a while. If the problem persists, it must come from the remaing devices (screen, mouse, keyboard). But then at least you have the start of a handle. If the problem does not manifest itself, then one of the disconnected devices is the cause. Those you can replug one by one and verify the effect.

Okay, thanks whs, i was trying to hold out on doing this for a while because the product is still under warranty (the seal isnt broken so I have not added anything new hardware wise) and has run fine for 6 months so I am resisting to look under the bonnet at the moment. The only thing I have updated is windows 7 from vista. My keyboard and mouse are wireless and the only connection is via a usb receiver which I have removed a couple of times to check. Therefore I can rule out the keyboard and mouse.

I recently installed a game (latest one) which can put a strain on the graphics card yet runs perfectly. It was a couple of days after I then received the problem. I will run the game and see what the GPU temp gets to, strange how it goes constant at idol though without running anything.

Okay while the game is running I get a 65% temparture reading from my graphics card, but I dont think that matters really I guess because the problem comes on when at idol.

65C is ok. That is not outside the norm. No need to open the box. Just play with your outboard devices - on/off, starting with the DSL. That would be my first suspect.

Okay I have disabled the network card and also played with the keyboard and mouse, the problem is still there but the interrupts have lowered to around 18% as opposed to 35%. Wierd. Do you understand what ACPI.sys is? that seems to be the thread in the system process that is taking up all this CPU usage (see screenshot). I have now attempted everything without opening the box.

I see only 2 other possibilities:

1. The ACPI.sys is corrupted. An sfc /scannow in elevated cmd may fix it.
2. Although very unlikely, it could be a virus. Check with Process Explorer that the path is
c:\windows\System32\DRIVERS\ACPI.sys Any other path would be suspicious.

Don't open the box. That will not give you any new leads.