Date: Thu, 22 Oct 1998 18:27:29 -0700 From: Mike Smith <mike@smith.net.au> To: Greg Lehey <grog@lemis.com> Cc: Mike Smith <mike@smith.net.au>, Jason Thorpe <thorpej@nas.nasa.gov>, Nick Hibma <nick.hibma@jrc.it>, FreeBSD hackers mailing list <hackers@FreeBSD.ORG> Subject: Re: multi-user: multiple consoles in FreeBSD Message-ID: <199810230127.SAA02423@dingo.cdrom.com> In-Reply-To: Your message of "Fri, 23 Oct 1998 09:35:12 %2B0930." <19981023093512.Q28824@freebie.lemis.com>
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> > Jason's gripe was that you con't have more than one video card because > > the second wants its VGA-compatibility registers mapped in the same > > place as the first. > > Right, but there are ways to disable it. Yes, although they're not in our hands. > > Unless there's something really odd going on, it's relatively > > trivial to simply map the I/O ranges for display cards other than > > the first somewhere else; you just need the smarts in your system to > > do this. > > > > Video chipsets not supporting this would be in violation of the PCI > > spec. I wouldn't expect this to be too common. > > Hmmm. How would you go about doing it? It would have to be in the > BIOS setup, and I can't see anything there that allows it. I suppose > you could start up with one video BIOS disabled, and then enable it > programmatically during the boot. There are several components which need to play "nice" for it to work. The system BIOS has to do the "right thing" when it's setting the PCI interfaces on the cards up; it needs to deal with the case where it's got more than one device that says it's a VGA adapter, and only map one of them in. If it's stupid it may crash or map them both (which would probably hang the bus). Then the BIOS on the card that doesn't have the compatibility mappings has to realise the fact. If it doesn't, it will try to talk to the registers as though they were for it, which would be bad. It might be less bad if all the cards were identical. Since Jason claims to have tested this and failed, while I know that you have at least one well-behaved card, it seems to be a bit of a mixed bag. I wonder if the current crop of ATI cards still work? I've got a pair of Rage 3DII's here I could try it with. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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