Date: Tue, 05 Jan 1999 15:31:21 -0500 From: "Louis A. Mamakos" <louie@TransSys.COM> To: Drew Baxter <netmonger@genesis.ispace.com> Cc: Terry Lambert <tlambert@primenet.com>, sthaug@nethelp.no, jamie@itribe.net, freebsd-hackers@FreeBSD.ORG Subject: Re: PnP PCI modem Message-ID: <199901052031.PAA39633@whizzo.transsys.com> In-Reply-To: Your message of "Tue, 05 Jan 1999 14:58:17 EST." <4.1.19990105145650.00bf39d0@genesis.ispace.com> References: <14757.915110288@verdi.nethelp.no> <4.1.19990105145650.00bf39d0@genesis.ispace.com>
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> At 07:54 PM 1/5/99 +0000, Terry Lambert wrote: > >> > So, does this mean motherboards with a decent number of PCI slots will > >> > start appearing? > >> > >> I wouldn't count on it - I think it's more likely that you'll see more > >> USB equipment. > >> > >> AFAIK it's rather difficult electrically to have more than five slots in > >> one PCI bus. Thus if you need more, you'll need a system with more than > >> one system bus to PCI bridge. Thus higher cost, lower volume. > > > >This is a current issue, and is related to the chipset. > > > >Apple has a good PCI chipset, as does DEC; I believe both support > >6 slots without a bridge because they have seperate lines for 6 > >slots. The Intel chips tend to have only 4 lines; some motherboard > >manufacturers double up one of the lines to get 5 slots. I suspect > >you could double up some of the lines on the DEC chip; don't know > >about the Apple. > > There are boards out there with 7 PCI slots that run Pentium II's. If I > remember right ASUS makes one, but don't quote me on that. It's very > likely it isn't using an Intel 440 chipset at all though, probably some > other company (BTC)? I find this board more practical now than I would say > 2 years ago.. Because 2 years ago I still had a lot of ISA hardware. The > only thing ISA now is my Sound Blaster AWE32. > The slot limitiation is mostly an electrical issue, having to do with bus loading issues. The PCI spec (which I don't have handy at the moment) presumes a certain number of loads; you have to count the devices on the card as well as the rather crummy connectors used. This is one reason why CompactPCI systems with their eurocard-style bus connectors can have more slots per PCI bus - the high quality connections present less of a capacitance load on the bus. I think that most AT-style boards with more than 3 or 4 PCI slots have some of the slots behind a PCI bridge, so it's really two busses. louie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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