Dell R805 owner manual Checking the Equipment, Troubleshooting IRQ Assignment Conflicts, 138

Table 4-1. Start-Up Routine Indications (continued)

Look/listen for: Action

The USB CD drive activity indicator. See "Troubleshooting a USB Device" on page 143.

The CD drive activity indicator.

See "Troubleshooting an SD Card or Internal USB Key" on page 152.

The hard-drive activity indicator.

An unfamiliar constant scraping or grinding sound when you access a drive.

See "Troubleshooting a Hard Drive" on page 155.

See "Getting Help" on page 175.

Checking the Equipment

This section provides troubleshooting procedures for external devices attached to the system, such as the monitor, keyboard, or mouse. Before you perform any of the procedures, see "Troubleshooting External Connections" on page 139.

Troubleshooting IRQ Assignment Conflicts

Most PCI devices can share an IRQ with another device, but they cannot use an IRQ simultaneously. To avoid this type of conflict, see the documentation for each PCI device for specific IRQ requirements. Table 4-2 lists the IRQ assignments.

Table 4-2. IRQ Assignment Defaults

IRQ Line	Assignment
IRQ0	System timer
IRQ1	Keyboard controller
IRQ2	Interrupt controller 1 to enable IRQ8 through IRQ15
IRQ3	Serial port 2 (COM2 and COM4)
IRQ4	Serial port 1 (COM1 and COM3)
IRQ5	Remote access controller
IRQ6	Reserved

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Troubleshooting Your System