5 HP BIOS

BIOS Addresses

 

There are three major interrupt modes available:

 

PIC mode: This “Legacy” mode uses only the interrupt controllers.

 

Therefore, only one processor can be supported in this mode. 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”. In the virtual wire

 

mode, only one processor executes operations.

 

Symmetric I/O mode: This mode is implemented using the I/O APIC

 

controller and allows for multiple processor operations.

 

 

NOTE

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 APIC bus to the processors.

 

 

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 page 59 for a table of the PCI device interrupts.

95