Date: Thu, 13 Nov 2008 15:03:53 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Joerg Sonnenberger <joerg@britannica.bec.de> Subject: Re: assigning interrupts Message-ID: <200811131503.53975.jhb@freebsd.org> In-Reply-To: <20081113154003.GC1750@britannica.bec.de> References: <491BFB68.7050405@infoweapons.com> <20081113104054.GA17501@icarus.home.lan> <20081113154003.GC1750@britannica.bec.de>
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On Thursday 13 November 2008 10:40:03 am Joerg Sonnenberger wrote: > On Thu, Nov 13, 2008 at 02:40:54AM -0800, Jeremy Chadwick wrote: > > Otherwise, consider purchasing a motherboard that has an APIC (this is > > not a typo) increasing the IRQ count to 256. > > This is wrong. The first IO-APIC gives you 8 additional interrupts to > the 16 ISA interrupt lines. Every additional IO-APIC gives you 24 more. > Most modern chipsets have one IO-APIC, at least for non-embedded > systems. It doesn't mean you don't get interrupt sharing though. I/O APICs are not hardwired to 24 pins. Early Pentium SMP systems actually only had 16 pins on their I/O APICs. I've seen I/O APICs with 32 pins, etc. There is a register in the I/O APIC that lets software know how many pins it contains. -- John Baldwin
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