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Subject:
From:
Will Stephenson <[log in to unmask]>
Reply To:
PCBUILD - Personal Computer Hardware discussion List <[log in to unmask]>
Date:
Mon, 3 Jan 2000 06:29:27 -0500
Content-Type:
text/plain
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text/plain (57 lines)
Hello!

This is a wonderful discussion. Twice, an "IRQ routing table has been
mentioned. What exactly is that and where can it be found?

Thanks!

Will Stephenson ><>
[log in to unmask]


PCI devices can share an IRQ, unlike ISA devices. Windows 98 can
dynamically assign PCI bus IRQs to PCI devices, using PCI bus IRQ steering.
If PCI bus IRQ steering is disabled in Windows 98, the BIOS will assign
IRQs to PCI devices, but if PCI bus IRQ steering is enabled, Windows will
assign IRQs to PCI devices. The "IRQ holder" is used to reserve the IRQ for
the PCI device(s), to the exclusion of ISA devices.

Check your BIOS' CMOS settings to verify that you have enabled a PnP OS
and/or, correct any errors in your IRQ routing table for the motherboard
(you might have to set an IRQ manually). Don't set any IRQ for PnP use if
the IRQ is used for a legacy/ISA device.

If that's not the problem, your IRQ Steering may be disabled in Device
Manager. Verify that the "Use IRQ Steering" check box is selected in device
by clicking:

   Start --> Settings --> Control Panel --> System --> Device Manager -->
   System Devices --> PCI Bus --> IRQ Steering

and see if the "Use IRQ Steering" box is checked (enabled). Also, make sure
that one or more valid IRQ routing tables are listed.

Sometimes, you have to apply a patch from the motherboard manufacturer.
Check your motherboard manufacturer's web site for updates.

Lastly, if you have a 486 computer, then its BIOS may not support PCI bus
IRQ steering. If you have Pentium II, then there will be support for it.
Your message was unclear which system you have.

CAVEAT: Unless you are adept at configuring CMOS and Windows settings (or
are bold and willing to learn the hard way) you probably shouldn't change
anything if all your devices are working properly (i.e., you have
sufficient IRQs for all devices).

HTH.

Regards,

John Chin
mailto:[log in to unmask]
http://www.digitalconcern.com

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