IRQ's in WinXP Pro SP2

[Sundiver]

Looking at my system Diag, I have five different devices including my vid card, sound card, modem and usb (several USB listings) all sharing IRQ 5. With all the IRQ's available is there any way to change them manually on winxp? Having all those devices on one IRQ can't be good can it?

[StarOfAfrica2]

Do you have an option in your BIOS for assigning IRQ's on any devices?

[Skuzzy]

Not good at all and no way to actually change them in XP, without removing them in the device manager, then shut off the computer, then move the device, or go into the BIOS setup and manually configure the IRQ's for the PCI/AGP bus.
While in the BIOS setup, disable any device(s) you do not need (i.e. COM, LPT, onboard video, onboard sound....) you are not using.  This frees up interrupts so they can be used by other devices.

Of course, if your motherboard has all these devices hardwired to that IRQ, you are pretty much hosed.

[Sundiver]

I don't at all mind doing it the hard way Skuzzy. Thanks for the info.

Originally posted by Skuzzy
Not good at all and no way to actually change them in XP, without removing them in the device manager, then shut off the computer, then move the device, or go into the BIOS setup and manually configure the IRQ's for the PCI/AGP bus.
While in the BIOS setup, disable any device(s) you do not need (i.e. COM, LPT, onboard video, onboard sound....) you are not using.  This frees up interrupts so they can be used by other devices.

Of course, if your motherboard has all these devices hardwired to that IRQ, you are pretty much hosed.

[214thCavalier]

Its standard practice for it to list them as sharing when using winXP.
You  only have control of this before you install an operating system.
There should be an option in your bios for plug and play OS.
Setting it to yes gives windows total control of all devices not needed for actually booting up.
Setting it to no the bios configures all the system devices and will give you control of some but not all assignments in windows.

Note, you should not alter this setting after having installed your operating system.

[Sundiver]

All that being said will the performance increase really warrant reinstalling the OS with non-PNP enabled?

[Skuzzy]

Some devices do not share interrupts well while others do.  However, there is some overhead for sharing interrupts.  The more in the chain, the longer the interrupt handling for each device in the chain will be.
You really do not want high data demand devices sharing interrupts.  It is just going to cause oddities.

Is it noticeable?  Most people, I find, have so much other software running on thier systems, it probably would not be noticeable.

The absolute best performance attainable will be done when every device has its own IRQ.  I look at it this way.  It's free performance, no matter how small the increment is.  But I am an engineer and we are a whacky lot.

[38ruk]

the only way i have installed win xp is in standard pc mode , you can also go into device manger and change the driver for computer to standard pc. that splits up the irq's , and stops xp from bundling  them up . now if you decide to go to DM and change the driver it will have to re recognize all the system devices , and there is also the chance you will have to do a clean install of XP.  if you do a clean install at the promt for the raid drivers during setup hit f5 and it will give you the option for standard pc.  here are my irq's in standard pc mode.

IRQ 0   System timer   OK
IRQ 1   PC/AT PS/2 Keyboard (84-Key)   OK
IRQ 4   Communications Port (COM1)   OK
IRQ 5   Realtek AC'97 Audio   OK
IRQ 6   Standard floppy disk controller   OK
IRQ 8   System CMOS/real time clock   OK
IRQ 9   Standard OpenHCD USB Host Controller   OK
IRQ 10   Standard OpenHCD USB Host Controller   OK
IRQ 11   RADEON 9800 PRO (Omega 2.5.97)   OK
IRQ 12   Microsoft PS/2 Mouse   OK
IRQ 13   Numeric data processor   OK
IRQ 14   Primary IDE Channel   OK
IRQ 15   Secondary IDE Channel   OK

the only down side to this is i have to hit the power button to turn the pc off ...... hope this helps <>   38

[StarOfAfrica2]

I had a problem with my system sharing IRQ's even though I had free ones.  When I changed to the MOBO I'm using now, I was able to make the system assign everything its own IRQ.  My BIOS has an option to assign IRQ's automatically (the default), or to assign them manually.  I choose Manual assignment, which basically turns off the MOBO's ability to assign any IRQ's, but then I dont actually set any of them.  Then when Windows XP boots up, it assigns all 16 of my IRQ's to uniqe devices.