How XP assigns IRQ?

From: Raj (Raj_at_discussions.microsoft.com)
Date: 10/13/04 

Date: Wed, 13 Oct 2004 14:25:00 -0700

Hello,

I would like to know how XP assigns IRQ for each devices that are on the
ACPI enabled system.

Let me explain my problem, I have a system where IRQ 7 & 11 are
free/available. When I plug 2 16-bit PCMCIA cards in its slots, OS finds it
and assigns 11 for one card and either irq 3 or 4 for another card that
conflicts with COM ports. why OS assigns irq 3/4 even though IRQ 7 is
available.

I could get rid of this conflicts if I do the following steps,
1. Assign IRQ 7 for COM port and boot the system. Insert one PCMCIA card.
2. Assign IRQ 4 back to COM port and boot the system. Insert the second card.

Now XP assigns IRQ 7 for the second one and no conflicts. Why its so? Is
it a BIOS issue or OS issue? Any soln?

 I tried with different types of 16-bit PCMCIA card from different vendors.
Still the same problem. When I tried to reinstall the OS with two PCMCIA
card inserted, I get blue screen.

Thanks in advance.

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