Date: Fri, 17 Jan 1997 11:03:41 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: smp@csn.net (Steve Passe) Cc: ken@housing1.stucen.gatech.edu, smp@FreeBSD.ORG Subject: Re: Adaptec 3940UW and SMP Message-ID: <199701171803.LAA08745@phaeton.artisoft.com> In-Reply-To: <199701170726.AAA15776@clem.systemsix.com> from "Steve Passe" at Jan 17, 97 00:26:39 am
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> > Well, the manual isn't very revealing about whether there are > > actually one or two PCI busses on the board. The 5th slot is a a "shared" > > PCI/ISA slot, and it also has an ASUS MediaBus connector in line with the > > PCI connector. Here's what the board manual says about slot 5 and > > interrupts: > > > > "IMPORTANT: PCI Slots 4 & 5 share the same IRQ. If using PCI cards on both > > slots 4 & 5, make sure taht the drivers support "Share IRQ" or that one > > card does not need an IRQ assignment. Conflicts will arise on PCI Slots 4 > > & 5 taht will make the system unstable." > > so it appears that you might be able to put the 3940 into slot4 and the > vga into slot5, the SMC in any of the others, and have 2 free, usable slots Or... 'make sure that the drivers support "Share IRQ"', and you will also solve the problem without any of this additional crap. One caveat: the system may not "know" a card is inserted in slot 5 if there is not a card inserted in slot 4 (depending on how frobbed together the hardware is). > so this is where I get a little confused... I thought in the past the > typical board limitation of 4 PCI slots was based on the LINE[ABCD] > situation. Early PCI MBs sometimes used LINEA for slot1, LINEB for > slot2, etc. I was thinking that now they route the LINEA pin from each > card to the LINE[ABCD] inputs of the PCI_ISA bridge chip, hence the magic > of the number 4. Is this so, or do these PCI slot/LINEA INTs go directly > to the MB ISA redirector hardware? If so, what is magic about 4 (slots)? > Stated another way, why does the 5th slot need to be shared? The LINE[ABCD] situation is not the reason. The reason for 4 slots is the bus drivers couldn't handle more than 4 sources/sinks on a single chip. It's true that some designs used one line per slot (a *good* idea, IMO, since it means you can skip the sharing decode in the non-bridged case, and get a bit more speed out of the thing by servicing multiple slots concurrently). However, those boards were generally from the Intel Server Division; the boards they sold to the public (ie: most of the early PCI machines from most of the systems vendors like Dell, Gateway, etc., but not Compaq) were from the Intel OEM Products Division. The OEM Products Division boards *always* shared the same INT between all the slots. This pissed me off enough that I delayed buying a PCI machine for a long time. It used to be that FreeBSD couldn't handle more than one PCI card in one of these machines because the drivers couldn't do "shared". Since the FreeBSD drivers have since been fixed, I don't understand the "conflict"... is it that there are one or more drivers that *haven't* been fixed? All of the drivers should be able to share interrupts. Regards, Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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