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#1 bigrobifer


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Posted 03 August 2014 - 05:20 PM

I have over 200 IRQ's listed in device manager. In system info several irq's aren't list (2-7 , 9-10 , 14-15, 20)  then the ones listed jumps from 23 (usb) irq device to 83 all the way to 190, all these are listed only as microsoft acpi-compliant system.

 Any thoughts or ideas on what could be doing this? And how.

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#2 Platypus


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Posted 03 August 2014 - 06:53 PM

I don't think you're seeing anything unusual, it's normal for the way Windows (or any protected mode OS) operates. Devices are virtualized in protected mode, so functionally the Device Manager is referencing little in the way of hardware IRQs. The Hardware Abstraction Layer creates virtual IRQs to access the devices on the system, and on a mainboard that implements ACPI (Advanced Configuration and Power Interface), Windows will have installed with the ACPI HAL, so the virtual devices will be ACPI devices.


The system I'm on at the moment doesn't have every possible hardware interrupt listed, it also goes up to 23 but the virtual IRQs start from 81. There are also some with negative IRQ numbers.


Edit: we also need to allow for legacy hardware that might not exist in a modern system, such as parallel port or FDD, thus will have no hardware IRQ assigned, and the IRQ channels that chain to the next controller (IRQ controllers are 8-channel). So for example IRQ2 normally has no device assigned because it chains to the second controller, and IRQ7 is the default for LPT1, which a modern mainboard usually won't have.

Edited by Platypus, 03 August 2014 - 07:59 PM.

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#3 bigrobifer

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Posted 04 August 2014 - 02:18 AM

ok Thanks that helped me understand a little better. I got 3 negative irq's i find with wmi but knew what they are for. The usb port would be where i think the majority of these come from then. 

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