From owner-freebsd-hardware Mon Feb 3 03:29:06 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id DAA23944 for hardware-outgoing; Mon, 3 Feb 1997 03:29:06 -0800 (PST) Received: from Sisyphos.MI.Uni-Koeln.DE (Sisyphos.MI.Uni-Koeln.DE [134.95.212.10]) by freefall.freebsd.org (8.8.5/8.8.5) with SMTP id DAA23938 for ; Mon, 3 Feb 1997 03:29:02 -0800 (PST) Received: from x14.mi.uni-koeln.de (annexr2-44.slip.Uni-Koeln.DE) by Sisyphos.MI.Uni-Koeln.DE with SMTP id AA29021 (5.67b/IDA-1.5 for ); Mon, 3 Feb 1997 12:28:51 +0100 Received: (from se@localhost) by x14.mi.uni-koeln.de (8.8.5/8.6.9) id MAA12619; Mon, 3 Feb 1997 12:28:19 +0100 (CET) Message-Id: <19970203122656.TL27173@x14.mi.uni-koeln.de> Date: Mon, 3 Feb 1997 12:26:56 +0100 From: se@freebsd.org (Stefan Esser) To: Andre.Albsmeier@mchp.siemens.de (Andre Albsmeier) Cc: freebsd-hardware@freebsd.org Subject: Re: 5 devices in 4 PCI Slots ? References: <199702021445.PAA28878@server.us.tld> X-Mailer: Mutt 0.59-PL19 Mime-Version: 1.0 In-Reply-To: <199702021445.PAA28878@server.us.tld>; from Andre Albsmeier on Feb 2, 1997 15:45:56 +0100 Sender: owner-hardware@freebsd.org X-Loop: FreeBSD.org Precedence: bulk On Feb 2, Andre.Albsmeier@mchp.siemens.de (Andre Albsmeier) wrote: > Hi, > > I am currently running 2.2 on a Chaintech P5 board which has 4 PCI slots > available. Two of them are used with two 2940 controllers and the third > is used with a 2-channel SMC-Ethernet Card. The dmesg is as follows: > > ahc0 rev 0 int a irq 9 on pci0:9 > ahc0: aic7880 Single Channel, SCSI Id=7, 16 SCBs > ahc1 rev 0 int a irq 10 on pci0:10 > ahc1: aic7880 Single Channel, SCSI Id=7, 16 SCBs > Probing for devices on PCI bus 1: > de0 rev 36 int a irq 11 on pci1:4 > de0: SMC 8434BT-CH1 21040 [10Mb/s] pass 2.4 > de0: address 00:00:c0:ba:73:e0 > de0: enabling BNC/AUI port > de1 rev 36 int a irq 12 on pci1:5 > de1: SMC 8434BT-CH2 21040 [10Mb/s] pass 2.4 > de1: address 00:00:c0:81:78:e0 > de1: enabling BNC/AUI port > > However, I want to add a third 2940 to the fourth PCI slot. Will there > be any problems with the interrupts? Will there be one interrupt > assigned two times. Does FreeBSD handle this case properly? 1) Two PCI interrupts will go to the same IRQ, and this will slightly increase interrupt overhead. You should try to reduce the cumulated sycles spent in the interrupt dispatcher by sharing interrupts between lightly loaded devices (or, rather: devices that generate interrupts only at a moderate rate, in the long term). The interrupt lines, that will actually be shared, depend on your particular motherboard. But it is most common to have IntA of one slot be IntB of its one neighbour, and IntD of its other neighbour. (In a way, you can imagine PCI Int lines to be connected "diagonally", wrapping around from IntD to IntA ...) 2) FreeBSD is expected to handle this, and each single case where it is found to NOT handle interrupt sharing should be reported as a bug! (BTW: You will find, that you will have TWO shared interrupts, since you alread have 4 PCI devices, and will have 6 ...) Gruss, STefan