Pi 3 HDMI mode problems

[Alan Corey <alan01346%gmail.com@localhost>]

I'm running 2016-05-14-netbsd-raspi-earmv6hf.img.gz on a Raspberry Pi
3b and it seems to almost ignore the video modes in config.txt.
Mostly it does 1920x1080@60 except sometimes it looks like the same
mode but out of focus.  The monitor (Dell s2409w) says it's
640x480@60.

My EDID is apparently not readable under Raspbian because unless I
specify a mode I get a black screen.  I normally use hdmi_group=2,
hdmi_drive=2, hdmi_mode=24 on the 3b but my model B was different.
I'm not sure how universal HDMI modes are, apparently not very.

I tried the group 2 mode 16 suggested in a comment in config.txt and
it gives me the same 1920x1080.  I've tried about 4 modes including
hdmi_safe and the numbers from what Raspbian defines that as, plus my
2/2/24.  I'm not sure how it can look out of focus on an  LCD monitor,
it looks OK with other things fed into it, including the Pi in
Raspbian.  Sometimes it's just not readable.  I can't ssh into it
because I can't read the interface name so I can set it to a usable
IP.

I've recently discovered the monitor says it's 640x480 though.  I've
had X running a couple times, the characters in xterm are hard to
read.  How can I have tiny characters yet the monitor sees it as
640x480?  Maybe a dot clock thing.  It's like looking at a photograph
of a 1920x1080 that's only 640x480, you can't actually read anything.

I've never used NetBSD before, but I've used OpenBSD for 15 years
(i386).  Unfortunately they won't touch the Pi because they don't like
the BLOBs.  This is my 2nd Pi, I got my model B in 2013 and ran
Raspbian and FreeBSD on it.

  Alan Corey

-- 
Credit is the root of all evil.  - AB1JX