Mike, "..just trying to understand..." [muliprocessors]
You operate on wrong premises. BIOS is not fooled by
anyone, nor sees/not sees something. BIOS is _controlling_
everything. However, it may fool user configuration menu
with stupid broken-english messages, that's right.
There are certain agreements between BIOS and OS on
how hardware is represented, called HAL - hardware
abstraction layer. For Windows to understand the
hardware, BIOS has to report it in certain ways.
In very superficial terms, the BIOS does the following.
When a MP system starts, it starts with a single
"bootstrap" processor selected randomly or else.
In i-x86 architecture, each processor has to have
a local APIC - Advanced Peripheral Interrupt Controller.
The controllers are connected via a separate few-wire bus.
Running on a single processor, BIOS searches for
other APICs through a sophisticated arbitration process
and enumerates them. Then it allocates
memory areas for each APIC (==processor), and places
individual interrupt/configuration routines and
semaphores. BIOS also fills in a special interrupt table
to be able to send messages via APIC bus, and initializes
every found AP (Application Processor) to a sort of
idle state. Then BIOS continues to use the bootstrap
processor to boot from storage media into OS. OS then
reads tables created by BIOS and schedules tasks/threads
to different processors accordingly.
If a processor (or half processor with hyperthreading)
has logically all these attributes (APIC address and
tables), it will be treated by OS as independent processor.
Effectivenes of this is a different matter.
Hope this helps,
- Ali |
