Vista IRQ management

[Dave]

My Vista resources map shows the below 3 internal devices on my Platinum P6N
SLI Platinum motherboard with an E6600 Core Duo Intel CPU sharing the same
IRQ "(PCI) 20". I have nothing plugged into any PCI slots. One graphics
adapter in the PCIe x16 slot.

- High Definition Audio Controller
- NVIDIA nForce 430/410 SATA Controller
- Standard OpenHCD USB Host controller

Why is this? Does it not matter anymore to share an IRQ rather than have a
dedicated IRQ? Why would PnP or ACPI or whomever not spread the IRQ's out
more?

I've also got a whole lot of IRQ's showing "(ISA) xx Microsoft
ACPI-Compliant System" which I'm guessing are unused IRQs.

I even have a couple IRQs showing (PCI) -2, -3 and -4 and don't understand
why some would be negative or why some are ISA and others PCI.

Where can I learn more about this and is this an issue?

Thanks,
Dave

P.S. I have cross posted this to general and hardware_devices.

 

[Rick Rogers]

Hi Dave,

IRQ 20 is a virtual IRQ created by the system to handle those devices, and
IRQ sharing has been the norm since Win98. While those particular devices
may be onboard, they still are on the PCI bus, which is why it shows that
designation. A negative number may result when the first bit is a 1 rather
than 0, the system is interpreting it as a signed number rather than
unsigned large number. Many virtual interrupt requests can be created to
handle the various pieces of hardware's demand for the cpu's attention. I
would only be concerned if system information shows a resource conflict.

--
Best of Luck,

Rick Rogers, aka "Nutcase" - Microsoft MVP

Windows help - www.rickrogers.org
My thoughts http://rick-mvp.blogspot.com

 

[Dave]

OK thanks. Perhaps does not matter with the newer integrated APIC rather
than the old cascaded PIC chips that could only do 15 interrupts total and
had to share. Still curious about what the ISA vs. PCI status really means
underneath. I show no conflicts but just thought it would be more efficient
for devices to have their own IRQ whether physical or virtual rather than
share.

I found this article
http://www.e-articles.info/e/a/title/IRQ`s-~-ISA-interrupts-versus-PCI-interrupts/
but it does not currently work as their database appears down.

Thanks,
Dave

 

[Dave]

Nevermind that article. It is talking about the real ISA and PCI boards from
way back. Makes me even more curious though why they still classify current
IRQs in that fashion...Dave

 

[Rick Rogers]

Hi Dave,

Not 100% on this, but I think that it shows that legacy designation because
of the range of the addresses used, not because it's actually an ISA device.
If you run msinfo32 and look at the hardware resources, you'll see that the
designation does not carry over here.

--
Best of Luck,

Rick Rogers, aka "Nutcase" - Microsoft MVP

Windows help - www.rickrogers.org
My thoughts http://rick-mvp.blogspot.com

 

[Steve Thackery]

I remember this issue coming up back in the days of NT4. Apparently it's by
design, and actually helps speed things up a bit.

All the advice back then was to leave well alone. It ain't broke, so
there's no need to fix anything.

Steve