More info can be found in [https://books.google.nl/books?id=TVzjEZg1--YC&printsec=frontcover "Pentium Processor System Architecture. Chapter 15: The APIC"]
== SIPI Sequence ==
The INIT-SIPI sequence is done by the operating system after the firmware already gives the first INIT signal. This example code from the [ Silcos Kernel http://wiki.osdev.org/Silcos_Kernel]