Internal HP docs on 9845 sys?

[F.Ulivi]

Hi everyone,

I've been working for the last few months on implementing the MAME
emulator of HP 9845B system.
In case you're interested, have a look at MAME development page at
https://github.com/mamedev/mame.
My emulator mostly works, the main missing thing now is the graphic
mode and the ability to load optional ROMs.
Anyway, I'm posting here because I'd like to ask you a few questions on
HP docs.
The last thing I worked on for this emulator is the "TACO" tape driver.
I reverse engineered it
entirely from sw & the (scarce) docs available enough that it works.
So here a few questions for you:
* Back in the days, what was the HP approach to document
internally-developped chips for its own
  sw developers? I mean, was there a kind of programmers' guide for TACO
chip? Is there any hope
  someone scanned it and made it available somewhere? I know that for
hybrid processors HP made
  an internal manual titled something like "how they do dat" manual...
* Just out of curiosity, what a big company like HP does with its
"historical" documents? Do they
  have an archive where they keep documents & sw from, say, the 70s? Or
do they throw everything away
  when there is some kind of company "shake-up" such as big layoff
phases, closing of a site, merging
  and splitting of divisions?

Thank you.

-- F.Ulivi