title: About the IO-APIC 82093AA
body: <p>I want to program the IO-APIC &amp; Local-APIC in my loader code, the code runs after BIOS.</p>
  
  <p>I've read the i82093AA datasheet, and found that the register base is defined by PIIX3's APICBASE register. How can I read the "PIIX3 APICBASE" register?</p>
  
  <p>As I know IO-APIC register base is 0xFEC00000 by default, but the BIOS may change it. So I want to find a way to get the base correctly.</p>