Date: Thu, 13 Nov 2008 18:34:52 +0100 From: Joerg Sonnenberger <joerg@britannica.bec.de> To: freebsd-hackers@freebsd.org Subject: Re: assigning interrupts Message-ID: <20081113173452.GA8646@britannica.bec.de> In-Reply-To: <20081113165631.GA26469@icarus.home.lan> References: <491BFB68.7050405@infoweapons.com> <20081113104054.GA17501@icarus.home.lan> <20081113154003.GC1750@britannica.bec.de> <20081113165631.GA26469@icarus.home.lan>
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On Thu, Nov 13, 2008 at 08:56:31AM -0800, Jeremy Chadwick wrote: > Regarding "it means you can still get interrupt sharing", I'd like to > hear more about why/how that's possible with a system sporting at least > one I/O APIC. You still have a limited number of interrupt lines. Many non-highend mainboards have 4 or 8 interrupt lines. You often have more than 8 PCI devices that want interrupts (e.g. VGA, audio, 3 USB controllers, 1 EHCI contoller and the SATA controller are enough to consume all lines). As soon as you now add a new network devices, you end up sharing PCI lines. The IO-APIC wiring is also often fixed, so it can't be controlled by software. Joerg
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