When the local APIC is enabled, the LINT[1:0] pins can be programmed through the APIC’s
vector table to be associated with any of the processor’s exception or interrupt vectors.
The LINT[1:0] pins are not available on the Intel486 processor and the earlier Pentium processors
that do not contain an on-chip local APIC. Instead these processors have dedicated NMI
and INTR pins. With these processors, external interrupts are typically generated by a systembased
interrupt controller (8259A), with the interrupts being signaled through the INTR pin.
(Intel486 和更早的处理器没有local APIC,中断号通过8259A控制,时钟中断是8号中断)