Framebuffer or standard VGA ?
ollie at sis.com.tw
Wed Sep 11 21:01:00 CEST 2002
On Wed, 2002-09-11 at 16:09, Peter Stuge wrote:
> On Tue, Sep 10, 2002 at 11:22:58PM -0700, 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? I don't understand your answer.
> > I thought most vga cards were register compatible with the legacy VGA
> > register set, only that there were a lot of other (sometimes secret) things
> > to setup. Is this wrong?
> That's Ollie's point AFAICS.
What is AFAICS ??
> > Fortunately regular vga cards are not very important to me, actually, I am
> > really most interested in integrated chipsets, such as the stpc and the via
> > apollo ple133 northbridge, both of which are legacy VGA register
> > compatible.
> In this case, when the chips really ARE VGA compatible, of course you can
> program the neccessary registers with appropriate values and get the
> expected results. You could try this for all graphics chips, just for fun.
> With a little luck it will work better than we expect.
> You will want to dump the VGA registers on a running system, and of course
> you're interested in 0x3c0, 0-0x14 at 0x3c0:0x3c0, 0x3c3, 0-4 at 0x3c4:0x3c5,
> 0x3c6-0x3c9, 0-8 at 0x3ce:0x3cf and 0-0x14 at 0x3d4:0x3d5.
The catch is, for most cases, you have to program those "non-standard"
undocumented extended register first then these Standard VGA registers
become "Standard". You can try it anyway.
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