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106 ST-133 Controller Manual Version 3.B
alternative I/O addresses and interrupt levels so that conflicts can be resolved. Software is
available to help identify specific conflicts.
The following example may serve to illustrate the problem. Suppose you had a system with
an ISA network card, a PCI video card and an ISA sound card. Further suppose that you
were then going to install a PCI Serial Buffer card. Before installing the PCI Serial card, the
I/O address and interrupt assignments for the installed cards might be as follows.
Slot Type Status I/O Address(s) Interrupt
1 (ISA) ISA Network Card 200-210 11
2 (PCI) PCI Video Card FF00-FFFF 15
3 (ISA) ISA Sound Card 300-304 9
4 (PCI) Empty N/A N/A
Table 9. I/O Address & Interrupt Assignments
Before Installing Serial Card
As shown, there are no conflicts, allowing the three peripheral cards to operate properly.
If the PCI Serial card were then installed, the BIOS would interrogate the PCI cards and
may reassign them new address and interrupt values as follows.
Slot Type Status I/O Address(s) Interrupt
1 (ISA) ISA Network Card 200-210 11
2 (PCI) PCI Video Card FE00-FEFF 11
3 (ISA) ISA Sound Card 300-304 9
4 (PCI) Princeton Instruments PCI
Serial Card
FF80-FFFF 15
Table 10. I/O Address & Interrupt Assignments
After Installing Serial Card
As indicated, there is now an interrupt conflict between the ISA Network Card and the
PCI Video card (both cards have been assigned Interrupt 11), causing the computer to no
longer function normally. This doesn't mean that the PCI Serial card is defective because
the computer stops functioning properly when the Serial card is installed. What it does
mean is that there is an interrupt conflict that can be resolved by changing the interrupt
level on the conflicting Network card in this example. It is up to the user to consult the
documentation for any ISA cards to determine how to make the necessary change.
Note: Changing the order of the PCI cards, that is, plugging them into different slots,
could change the address and interrupt assignments and possibly resolve the conflict.
However, this would be a trial and error process with no guarantee of success.
Diagnostics Software
Many diagnostics programs, both shareware and commercial, are available to help resolve
conflicts. Most often, all that's required is a program that will read and report the address and