Date: Wed, 18 Jul 2007 03:33:31 +0200 From: Fredrik Tolf <fredrik@dolda2000.com> To: freebsd-questions@freebsd.org Subject: OT: PC VGA Message-ID: <m3wswyijh0.fsf@pc7.dolda2000.com>
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Hi all! My apologies for posting off-topic to this list, but I really can't think of whither I *should* turn this question, and I think there ought to be people here in the know. The thing is, I've been wondering for the longest time how PC VGA really works. In particular, I'd like to know the mechanism that allows some random PCI card to be accessed through the standard VGA register addresses (0x3c0 and its ilk) and likewise for the VGA BIOS and the real mode "framebuffer" memory mapping, and also what software entity that sets that stuff up. Any links would be highly appreciated! The practical reason why I'm wondering these things is because I'm using several video cards in one of my computers, with one X.org server for each card, and every once in a while, it causes problems which I'm guessing is because one of the "secondary" (non-VGA-mapped) card's BIOS is trying to access the card through the normal VGA ports and accidentally hitting the VGA-mapped card. I am also more generally curious about what it takes to use several video cards independently on today's machines. But I'm holding a general interest in these things, so I'm not just wondering for pragmatical reasons. Also, in general -- are there any good web resources for these sorts of things (hardware standards in general)? I've been googling around quite a bit without being able to find anything good. I'd appreciate any replies! Fredrik Tolf
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