Framebuffer or standard VGA ?
ollie at sis.com.tw
Wed Sep 11 20:42:00 CEST 2002
On Wed, 2002-09-11 at 15:55, Antony Stone wrote:
> On Wednesday 11 September 2002 7:22 am, Steve M. Gehlbach wrote:
> > > > Maybe someone knows if alphanumeric mode setup is via the standard VGA
> > > > register set on most modern VGA cards.
> > >
> > > I am afraid your are wrong. For modern VGA cards, there is actually no
> > > alphanumeric mode. These alphanumeric mode were simulated by BIOS or
> > > drivers. The worst thing, if you have no documents about these extended
> > > registers, you have no way to drive the clock gen for Dot clock, Hsync,
> > > Vsync.
> > Are you saying that it is not possible to use a text console with Linux
> > (vgacon.c) with modern VGA cards (BIOS mode 3)? Only framebuffer? Or are
> > you saying that without extra information (ie, the BIOS or the manuals) you
> > can't init it into mode 3?
> Excuse the second posting to this thread so soon after my last, but I've
> found a far more succinct way of expressing my point:
> If I go out and buy the latest whizz-bang graphics card, just released onto
> the market, and plug it into my three year old PC, whose designers knew
> nothing abut today's graphics cards, I expect to see a text console screen
> when I turn it on.
> This means one of two things. Either:
> 1. there's a standard way for the motherboard Bios to initialise _any_
> graphics card, so it can initialise a new one it's never heard of before (and
> presumably LinuxBios could do the same), or:
> 2. there's a standard init call to the bios chip on the graphics card, which
> knows how to set up that particular model, which again LinuxBios could
> perform in exactly the same way when it starts up ?
> Is there a flaw somewhere in my reasoning ?
The flaw is the these standard are "Legacy BIOS standard". You have to
provide various legacy BIOS functions since these VGA BIOS/init stuff
will call back to system BIOS. LinuxBIOS just doest not or incompletely
support these functions.
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