port-sparc64/55173: NetBSD-9.0/sparc64 blackscreens on bootup from CDROM on Sun Ultra 5

[lorenzocauli162%gmail.com@localhost]

>Number:         55173
>Category:       port-sparc64
>Synopsis:       NetBSD-9.0/sparc64 blackscreens on bootup from CDROM on Sun Ultra 5
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-sparc64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Apr 13 20:15:00 +0000 2020
>Originator:     Lorenzo Cauli
>Release:        9.0
>Organization:
>Environment:
>Description:
I have a Sun Ultra 5 with a UltraSparc II+ 360MHz and 256MB of RAM.
I burn the ISO to a CD, put it in the machine and at the openboot prompt I run 'boot cdrom'. The bootcode loads up and some kernel messages can be seen.
At one point though, when the "" is printed on console, the screen goes black, with all monitors tested reporting no signal, the keyboard stops working (status lights dont work, Stop-a doesnt work) and I can hear no seeking noises from the CD drive. I know it works because I used it to install Solaris multiple times and it always worked. The serial console doesn't print anything when the screen goes down. I have a friend with similar specs (512MB of RAM instead of 256, everything else is the same. even the HDD model) which has had the same exact problem.
I have made a video public on youtube describing the issue: https://www.youtube.com/watch?v=vVXH6TgBaFg
>How-To-Repeat:
1) Burn an ISO of NetBSD-9.0/sparc64
2) Boot it from OpenBoot with 'boot cdrom'
3) Wait for the kernel to load up and execute
4) Wait for it to just shut video down.
>Fix: