On Mon, 16 Feb 1998, Michael R Zucca wrote:

> > >   
> > > + 		#if 0
> > >   		if (sense == 0)
> > >   			found = 0;
> > > + 		#endif
> > 
> > I've seen this mentioned before. If you have a machine which reports '0'
> > when there is in fact a screen, what does it report when there's no
> > screen? Or, how does it report no screen? It sounds like the problem's
> > just different machines have different "no screen" reporting styles.
> 
> The Quadras, unlike the II's, support extended sense codes. Checking if
> a monitor is connected is more than simply checking if the sense register
> is a certain value.
> 
> What you do is you reset the sense lines to get a base sense code. Then
> you pull one line hi and collect the bits from the other two lines for
> each of the three sense lines. Bit shift the values and OR them together
> using the right incantation and you have an extended sense code.
> 
> The base plus extended sense codes tell you what monitor is connected, if
> any, to your monitor port.
> 
> The trouble with checking if the sense register is zero is that when MacOS
> is collecting its sense info, the last part of the extended sense code
> could have been zero. That value sticks around past NetBSD boot and suddenly
> we think there's no monitor. Not good :-)

So what you're saying is that we won't handle extended codes right.
Wouldn't a better fix for things be to indicate what models support
extended sense codes (in the machdep stuff), and change this test for
those models?

Can we support reading the extended sense codes before we get the intvid
stuff? If so, can't we just hack on the sense code reading code so we read
the right thing?

Take care,

Bill