[Open-graphics] Jumper count to disconnect DDC from DVI connector

[Timothy Miller]

On 9/7/06, Dieter <netbsd at sopwith.solgatos.com> wrote:
> >    To answer an earlier question: if we want to include a feature on OGC1 to disconnect the DDC signals from the DVI conne
> >ctor so that the external tool will have control of those signals, only two lines need to be disconnected: SCL and SDA.  So
> > the cost impact of doing it with jumper plugs would be minimal.
>
> If Jack's design is used, (and if I understand it correctly) I think we
> could look for a signal on the aux DDC, and if one is found then use it,
> If no signal is found on the aux DDC, then look for a signal on the
> DVI's DCC pins.  If this scheme works, then we don't need jumpers for DDC.

That is an interesting thought.  Just provide secondary DDC signals
that we probe first.  Adding extra pins is always a concern, however,
because signals from BGAs are hard to route.  Were it not for the
density of pins on the 3S4000, OGD1 could have fewer layers.  In fact,
we have inaccessible pins due to the fact that we don't have enough
layers to route to the inner-most balls.  I would not begrudge 4 extra
pins, however, so it's something we'll consider.  Indeed, we may find
it easy to add the pins but find them too costly to route to.  If we
add them at all, we'll add them to the inner-most set of balls on
TRV10.