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IRQ Conflict
abNORMal Dec-07-00 03:05 PM

I am STILL trying to resolve a lockup problem and I believe it's isolated to a soundblaster live! value card and a SCSI CD-RW. I have the following IRQ assignments:

IRQ Device
1 Keyboard


3 Universal Serial Bus Controllers
Universal Host Controller

4 COM1 (Bios says IRQ4 is Serial Port A)

6 floppy

7 LPT1

9 SCSI Host Controllers
SCSI Host Adapter

10 modem

11 Display Adapters
Realtek ethernet controller
Sound Video and Game Controllers
SB Live! Value

12 Mouse


14 ATA Storage Controller
Primary IDE Controller

15 Secondary IDE controller

I see on your FAQ page that IRQs 9 and 11 "should be" free. How do I get it to redirect devices to available IRQs? (sound card to IRQ 5, for instance)

Notice I have 3 devices on IRQ 11, and the SCSI host adapter is showing up in IRQ 9.
Why is it forcing these devices to already-assigned IRQs, while leaving others free?


1. RE: IRQ Conflict
lbyard Dec-07-00 06:12 PM
In response to message 0
Go into the Windows Control Panel, System, Device Manager, PCI Bus, IRQ Steering and be sure it is enabled. You will need it with the number of devices you have it to share PCI bus IRQs. If not, go into the motherboard CMOS Setup and enable O/S is PnP aware. See Microsoft Knowledgebase Article Article ID: Q182604, Description of PCI Bus IRQ Steering at http://support.microsoft.com/support/kb/articles/Q182/6/04.ASP?LN=EN-US&SD=gn&FR=0&qry=IRQ%20steering&rnk=3&src=DHCS_MSPSS_gn_SRCH&SPR=W98 and Article ID: Q182628, How to Disable PCI Bus IRQ Steering in Windows (don’t disable it) at http://support.microsoft.com/support/kb/articles/Q182/6/28.ASP?LN=EN-US&SD=gn&FR=0&qry=IRQ%20steering&rnk=4&src=DHCS_MSPSS_gn_SRCH&SPR=W98, and, as you done, our FAQs on IRQs at http://duxcw.com/faq/irq/irq.htm for more info. While you are in the CMOS Setup disable all motherboard resources that you are not using that require an Interrupt; e.g., COM1: If you have a motherboard with a VIA chipset, download (http://www.viatech.com/drivers/index.htm) the VIA 4-in-1 driver set and install the IRQ Routing Driver. You may be able to assign specific IRQs to specific PCI slots in the CMOS Setup. Try to avoid using the PCI expansion board slot (usually numbered slot 1) adjacent to the AGP slot. Many motherboards use the same IRQ for PCI slot 1 as they do for the AGP slot and that can cause problems. I have omitted some tricks of the trade here that require more extensive treatment and plan an article on this basic computer troubleshooting art. I emphasize the words “tricks” and “art” and will emphasis it that way until such time the vendors that make the hardware and software for today’s PCs get there act together on this most frustrating problem and make it a science. As it is, PnP means Plug ‘n’ Prey. Larry

2. RE: IRQ Conflict
jwey Dec-13-00 08:44 PM
In response to message 0
Hi Larry,

I think I might have a similar problem. It appears that my video card (Hercules Dynamite TNT 16MB) and my sound card (Guillemot MUSE PCI) sometimes seem to "fight" each other, so to speak. My question: How do you find out what devices are assigned to which IRQs? I think perhaps my video and sound card are on the same IRQ, possibly causing the conflict.

John Wey

P.S. By the way, your review of the Antec KS282 case was absolutely excellent! I got one of these cases and it is the all-time best case I have ever had (I've had an Enlight--so-so--and a generic brand, pop rivets and all). With two of Antec's ball-bearing case fans installed I'll probably never have to worry again about any kind of heat problem. Thanks again for a great review.

3. RE: IRQ Conflict
lbyard Dec-13-00 09:26 PM
In response to message 2
I am happy that the review was useful... One way, to see what IRQs are assigned to what, is to click Start, Setting, Control Pane, System, Device Manger, double click the Computer, and select Interrupt request (IRQ). Although IRQ conflicts are the most frequent, Input/Output port address and DMA conflicts are possible and cause similar problems. Sound card DMA conflicts happen once in a while. Larry

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