[LinuxBIOS] MB1030 / 3036 VGA comes up :D

Stefan Reinauer stepan at coresystems.de
Tue May 2 22:56:54 CEST 2006

* Christian Sühs <chris at suehsi.de> [060502 23:12]:
> >>inb(0x03da) = 0xff
> >>inb(0x03da) = 0xff
> >>inb(0x03da) = 0xff
> >>inb(0x03da) = 0xff
> >>
> >>// after her always the same inb line
> >
> >it waits for a vertical blank interrupt which never happens.
> >At this point it probably expects the video to become light.
> But what means never happens? It happens after 20s without debug under 
> LB or immediatly without debug under testbios. After that it takes the 
> second run with longer delay.
Ah, sorry, I thought when you enable the output of inb(0x03da) = 0xff
it would not come to an end but print always the same inb line.

So it works when you enable above debug and wait long enough?

> What causes the vertical blank interrupt?

When the ray moves from the end of the screen to the beginning there's a
time frame which can safely be used to update the screen without any
flickering, thats the vertical blank. Its actually not an interrupt
because in above example the bios polls for that event rather than
getting an interrupt when its there.

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