Re: TGX Plus on sun4c (IPX) problem

[Julian Coleman <jdc%coris.org.uk@localhost>]

Hi,

> Maybe try older NetBSD?  I run 1.4T on my SPARCs; you might not want to
> (and might not need to) go that far back, but it might be worth trying
> a few older versions.

This is a good idea, just to eliminate any recent changes - maybe 8.x to
start with?

> It's _possible_ that the kernel cg6 setup tickles a bug - or a hardware
> fault - in your framebuffer in a way that Solaris X doesn't, but I
> consider that relatively unlikely.

I was looking at this, however:

  - we don't do any video (timing) setup for cg6, although we do make
    some changes e.g in cg6_reset [*]
  - the problem happens when the kernel starts printing, not when the
    framebuffer is attached, as below:

> > However trying to boot NetBSD 10.1 - the kernel spins its numbers, and as soon
> > as it would have started displaying boot info - the monitor resyncs (?) and the
> > screen goes white.  No disk activity after this.  I can only assume it’s locked
> > up.
> >  
> > I also tried this in stock “screen” setenv (i.e. 1152x864) and get the same
> > behavior.

This seems like the problem is when the kernel starts to output text.  The
spinning part should be output by the bootloader which then hands over to
the kernel.  I'm puzzled though, because the bootloader uses the PROM input
and output routines and the kernel does too until the keyboard/screen or
serial console are attached.

> Do you have any other 4M cg6s?  How do they behave in this regard?

The Sun4c Handbook only notes 501-1645 (GX CG6) but the page for
501-2253/501-2955 notes 4/50 (IPX) and 4/75 (SS2) in its list, so it should
work in these, and it does in Solaris.

Regards,

Julian

[*] https://nxr.netbsd.org/xref/src/sys/dev/sun/cgsix.c#cg6_reset