On 08/19/2010 05:52 PM, malc wrote:
Yes, but the programming model was different.
Look at the PIC compared to the lapic. The PIC is programmed via pio at a
fixed location. There is only one PIC and it interacts with the system just
like all other devices. IOW, there is no reference to CPUState.
There are two PICs actually there's a cascade..
Technically speaking, originally there was just one and then more IRQs
were supported by cascading and reserving an IRQ line for supporting
cascading. I think you can technical cascade with any IRQ and have more
than one slave but the historic PC architecture only had one slave AFAIK.
Regards,
Anthon Liguori
When you look at the local APIC (apic.c) however, you see that it's the only
device in the tree that actually interacts with a CPUState. The notion of
cpu_get_current_apic() is a good example of the tricks needed to make this
work.
The local APIC is a cpu feature, not a device.
Regards,
Anthony Liguori
