GE VR11, Reference Manual

Page: 66 / 118

GE Intelligent Platforms – VR11, VP11 Hardware Reference Manual, Second Edition Page 66
APIC Controller
The VR11 supports APIC (Advanced Programmable Interrupt Controller). This
handling of the APIC interrupt services must be supported by the operating
system. The I/O APIC handles interrupts very differently than the 8259.
Briefly, these differences are:
•
Method of Interrupt Transmission.
The I/O APIC transmits interrupts
through processor FSB, and interrupts are handled without the need for the
processor to run an interrupt acknowledge cycle.
•
Interrupt Priority.
The priority of interrupts in the I/O APIC is independent
of the interrupt number. For example, interrupt 10 may be given a higher
priority than interrupt 3.
•
More Interrupts.
The three I/O APICs in the VR11 support a total of 28
independent interrupt sources.