Re: Chumby NeTV?
Adding "support" for 1080p60 is technically a matter of adding its mode to the timings file and recompiling. I forget what the exact numbers are, but if you run "killall matchmoded; matchmoded --debug" and switch the input to 1080p60, it'll print out [roughly] the right numbers. You can then add those to the timings header file and rebuild, or write a program that simply opens up /dev/fb0 and sets those numbers manually.
The problem is that the FPGA just can't keep up with that resolution. The link is not stable -- you'll see it show a few frames of video, then the screen will go dark, then show a few more frames. Worse, there tends to be a lot of smearing and sparkle on the output. There's no real danger from overclocking, it just doesn't look good at all, assuming it even syncs.
It works without an input. When it first boots, it's running a version of the FPGA file that only does output, because the bootloader doesn't have the knowhow to negotiate the HDMI link. If it detects no display connected, or if it detects an unsupported mode, matchmoded will call switch_to_720p() and change the display to generate an unencrypted 720p image rather than attempt to overlay on top of an unsupported signal.
Incidentally, an early version of matchmoded is still present in the source tree. matchmode was a binary that used to get invoked when a udev event was triggered, usually by a hotplug event. Rather than using a lookup table of modes it would query them from the current timing settings in the FPGA. As such, if you wanted to give 1080p mode a whirl you could compile that, copy it over to your NeTV board, kill matchmoded, and run matchmode a few times until you get stable timing numbers.