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Using System Resources
Most ISA devices installed in the system require you to reserve an IRQ. PCI devices also
need to use an IRQ, but since they share system resources they can use the same IRQ. At
least one IRQ must be left unassigned, for use with any PCI devices installed in your system.
The system has a limited number of open IRQs. To install more ISA devices than you have
open IRQs, you must disable one unused system port for each excess ISA device, unless the
device does not require an IRQ.
To reserve an IRQ for an installed device:
1. Restart the system and start the BIOS Setup program.
2. On the PCI/PnP screen, select the IRQ you want to reserve.
3. Change the setting for the selected IRQ to ISA/EISA.
4. Save the changes and exit from the BIOS Setup program.
The following expansion cards require specific system resource settings, as noted:
Expansion card
(installed in the system)
Resources
required
BIOS Setup
parameter settings
First modem (Windows NT) COM3, IRQ 4 Disable serial port 1 (COM1);
reserve IRQ 4
First parallel printer adapter Base address 278 None
Second parallel printer adapter Base address 3BC None
3Com network adapter IRQ 10 (default) Reserve IRQ 10
On a system running Windows 95, ensure the following system resources are set as noted:
System resource
BIOS Setup parameter settings
Plug and Play operating system On the PCI/PnP screen, set Plug and Play Aware O/S
to Yes
Serial port 1 COM1 Reserve IRQ 4 (if port is to be used)
Serial port 2 COM2 Reserve IRQ 3 (if port is to be used)
Parallel port LPT1 Reserve IRQ 7 (if port is to be used)
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