Philipp Thomas wrote:
Dual boards have a so called APIC (Advanced Programmable Interrupt Controller), these offer 256 IRQs at maximum. The kernel makes use of them for instance to reroute shared IRQs so that each device has its own. There's nothing wrong with devices sharing an IRQ, but it's easier for the kernel to identify the source of the IRQ.
Yes everything still works with shared IRQs but I absolutly get a performance hit because of it. Even on my boxes that have APIC. It seems to me that a SMP box with APIC should never have to share IRQs yet all mine seem to. I still have to arrange things "slot" wize to make sure the ones I want unshared are unshared. Even bios settings don't seem to help. When I goto "K"-"Preferences"-"information"-"interrupts" can I assume the information I get is correct when it says I'm sharing an IRQ between multiple boards even thoug my box is SMP/APCI? If this info is acurrate how can I make the kernel "UNSHARE" the IRQ's?
UP boards normally don't offer an APIC, so you're limited to the classic 15 IRQs. Now some UP boards do feature an APIC, that's why there's an option in the kernel configuration to enable it.
Philipp
-- Mark Hounschell dmarkh@cfl.rr.com