HP Vectra VL800 Technical Reference Manual page 121

NOTE
There are three major interrupt modes available:
• PIC mode
This "Legacy" mode uses only the interrupt controllers. This mode can be
selected upon installation of Windows NT.
• Virtual wire mode
This mode is implemented using the 82C59 interrupt and the I/O APIC
controller and is used during boot time. The virtual wire mode allows the
transition to the "symmetric I/O mode".
• Symmetric I/O mode
This mode is implemented using the I/O APIC controller.
In "PIC mode" and "virtual wire mode", the PCI interrupts are routed to the
INT line. In the "symmetric I/O mode", the PCI interrupts are routed to the
I/O APIC controllers and forwarded over an GTL bus to the processor.
PCI Interrupt Request Lines
PCI devices generate interrupt requests using up to four PCI interrupt
request lines (INTA#, INTB#, INTC#, and INTD#).
PCI interrupts can be shared; several devices can use the same interrupt.
However, optimal system performance is reached when minimizing the
sharing of interrupts. Refer to
interrupts.
page 74 for a table of the PCI device
6 HP BIOS
BIOS Addresses
121