Strange graphics issues on G5 with NVIDIA 6600

[Julio Merino]

Hello all,

It has been a long time since I touched FreeBSD last... but I recently got
a PowerMac G5 (because!) and FreeBSD seems to be the only reasonable choice
these days for such a machine. So... I'm back here :)

First of all, and to be honest, everything has worked better than expected.
I could get the system installed without trouble and I've been surprised to
see that there are now pre-built binary packages for powerpc64 available
out of the box! A very nice surprise. Last time I tried this on a similar
machine 7 years ago, I remember having to build a ton of stuff from
scratch, which wasn't fun...

So... I have installed X.org and, on the first attempt to run it, I got the
following video output:

https://photos.app.goo.gl/R1bx4FCRD7aRKG9x9

Note that the colors are all off and that half of the screen is "strange":
the background is split in two colors. This picked up the scfb driver.

This machine comes with an NVIDIA 6600, so I manually installed
xf86-driver-nv to give it another try. With the nv driver, I got this:

https://photos.app.goo.gl/U7Yx3zs2YfND25ks7

In this case, the colors are good and things mostly work... but note that
the background problem is still there. And if I maximize something like
xterm, the same thing happens: the top of the window has the right white
color, but more than half is black and has some rendering artifacts:

https://photos.app.goo.gl/kWacbVNXAB8cpqHJ9

Lastly, with the nv driver, when I exit Xorg I'm left with a console with
extremely faint text. There is no brightness.

Here is the X.org startup log: https://pastebin.com/srgPiUiu

Any thoughts or things I could try? I remember the other machine I had
years ago had this same card and gave me some trouble too, because I
remember buying a Radeon to replace it. Maybe I should do the same thing
now? :-/

Thank you!

-- 
jmmv.dev