HP-21MX bootstrapping?

Brent Hilpert hilpert at cs.ubc.ca
Wed Feb 20 01:21:37 CST 2008

Tim Riker wrote:
> As you likely saw, I posted a source version of your ascii loader. What
> differences does your assembler have?
> The loader has no license info. I presume it's ok for me to post my source?

I would just suggest that you add a log/history comment with date/name under my
creation date/name comment to indicate changes and to distinguish it from my

> > Another possibility might be to modify the old HP teleprinter loader:
> >
> >   http://www.cs.ubc.ca/~hilpert/e/HP21xx/software/bblteleprinter.html
> I'll look into this as well. Thanx!
> > It uses the HP BBL load format.
> Not sure what this is. Can you point me to any docs?

The format is documented (or at least my understanding of it) at the
beginning of the above-linked file, based on my disassembly of the
machine code in the HP manual. Look at the other two period BBLs on my
site for comparison.

Actually, to be a little more accurate in terminology: the BBL (Basic Binary
Loader) bootstrap programs read data in ABS (ABSolute-address load record)
format. BBL & ABS date from the original 2116 systems. Originally the BBLs were
manually toggled into core at the top of memory.
ABS format (.abs) does require a fully-transparent, 8-bit, binary datapath.
There was also a relocatable record format usable at later stages in the bootstrap.

I believe the ABS format, with new BBLs for new devices, continued to be used with
the later 2100 systems but others can comment on that better than I can.

> > It was for loading over a serial line from the paper tape reader on a teletype,
> > but uses a 12531A IO interface, which was a bit-bang interface. It could be
> > converted for the 12531B/C by, in short, replacing the ReadByte routine with
> > instructions appropriate for the 12531B/C.
> ok

I will hazard a guess that if an HP serial-line loader for the 2100 shows
up it may look a lot like what I'm describing in modifying the old teleprinter loader.

> > (Also note that my experience in this is limited to playing with a 2116 system).
> lucky dog. :)

Didn't you have a 2116B with a broken aluminum frame, or was that someone else?

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