Local APIC support on uniprocessors

configname: CONFIG_X86_UP_APIC

Linux Kernel Configuration
└─>Processor type and features
└─>Local APIC support on uniprocessors
In linux kernel since version 2.6.12  
A local APIC (Advanced Programmable Interrupt Controller) is an
integrated interrupt controller in the CPU. If you have a single-CPU
system which has a processor with a local APIC, you can say Y here to
enable and use it. If you say Y here even though your machine doesn't
have a local APIC, then the kernel will still run with no slowdown at
all. The local APIC supports CPU-generated self-interrupts (timer,
performance counters), and the NMI watchdog which detects hard
lockups.