Sun Open Firmware - insiders?

[der Mouse]

> I have a question regarding Sun OpenFirmware that's been bugging me
> for some time now.  [...]

> What I'm imagining here is to have a look at the code that is
> responsible for the netbooting operation of the Sun.  Why does it
> have to obtain the machine's IP, that of the tftp server and what
> else via rarp?

It can't obtain anything but its own address via rarp.  It normally
gets its TFTP server's address via bootparams, I think, at least for
older machines (newer ones may use something else for all I know).
It's possible that it initially queries whoever answered its RARP, but
if it gets no answer it broadcasts the query - and I think it
broadcasts the TFTP request too if necessary.

> I'm by no means a Sun expert yet, but as I've understood it, you can
> define your own FCode commands and store them in NVRAM, so one could
> modify the boot code to use parameters stored in environment
> variables, either if a flag "use-stored-IP?" is set or as a fallback
> if there's no rarp server around.

Yes, except that the space available in the NVRAM is fairly limited as
I understand it.

> I've already got myself a Forth book and the FCode manuals from Sun,
> and I had a look at some commands with "see".  "see" however often
> spits out hexadecimal codes in parenthesis amidst of Forth words and
> I've yet to understand what they mean;

They appear to be some kind of headerless something.  There's one of
the words internal to see that can deal with them - (see or some such -
and you can use it as in

ok see foo
... (f28470c0) ...
ok f284709c0 (see
... that word ...

(or whatever the internal word is - it's visible in "see see").

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