On 8/29/07, Fredrik Tolf <[EMAIL PROTECTED]> wrote: > > Thanks for the tips, both of you! If have actually already ordered the > > book that Timothy linked to. > > The book arrived today, and I now understand a *lot* more about PCI than > I did previously. Thanks again!
Sweet! Now we can apply some more eyes to our PCI controller design. > > This might not be the place for these things, but if you don't mind > spending a little time on me, there's still something I don't quite > understand in relation to VGA legacy address decoding. Namely, how does > the system select which card is supposed to do legacy decode? This is definitely the right place. We need VGA emulation. If there's a standard way to enable/disable VGA legacy decode, I don't know about it. I've seen cards with a physical jumper. But what I think is more common is that VGA is enabled in a device-specific way by the VGA BIOS code. The system BIOS finds the first VGA-capable card and runs its BIOS code, and that code will switch on the decode in our device. > > Since it is usually selectable in the system BIOS UI which card should > be initialized as _the_ VGA card in the presence of multiple > VGA-compatible cards, there has to be some standardized way of enabling > legacy decode on a card, right? Possibly, but a lot of "standard" things are only standardized by the fact that there's a hook provided by the peripheral's firmware. > I just can't find what that way is. My > naive guess is that it might be that the system BIOS only calls the VGA > BIOS code for the selected card, and it sets up legacy decode in a > card-specific way, but I can just find no way to confirm that, and I've > been googling for quite some time now. Time to disassemble someone's BIOS code and find out? :) Note that anyone who does that needs to be careful about how they contribute to developing a new BIOS, because we don't want to be accused of stealing code. -- Timothy Normand Miller http://www.cse.ohio-state.edu/~millerti Open Graphics Project _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
