Question re TM11 boostrap

[Tim Shoppa]

> Several people have asked for a bootstrap for the TM11 magtape. V2.3a
> has a simple bootstrap that just reads the first magtape record and
> jumps to it.  However, John Holden points out that the M9301 bootstrap
> actually skips the first record and reads the second.

It depends on which OS (and version) you're using, but most of
DEC's later OS's made some attempt to have bootable tapes be
ANSI-labeled volumes.  This meant that the boot block had to come
after the VOL1 header.  See, for example, the source code to
RT-11's DUP utility.

> Does anyone have source code for an actual TM11 bootstrap?

I certainly have some boot ROM's that I can disassemble.  I'll
also check my DEC manuals for the toggle-in bootstraps.

I know that in some cases it was necessary to re-execute the toggle-in
bootstrap if the real boot block was the second file/record.

Also note that it wasn't until the late 70's/early 80's that DEC
adopted the "second block is the boot block" strategy.  You're
likely to see different things depending on when a bootstrap was
written.

> What do the various versions of UNIX expect in a bootable tape image,
> particularly BSD 2.9 and 2.11?

2.11 plays it safe by putting down two copies of the boot block at
the beginning of the tape, each ending with a filemark.

All Q-bus tape bootstraps that might reside in a 11/53's console firmware
would be looking for the boot block to be the second block on tape.  But
as the TM11 wasn't a Q-bus device I don't think the 11/53 firmware is
going to resolve this issue.

A side comment on the emulator:  Have you ever considered putting the
11/53 firmware into your emulator, so that users can use the bootstraps
and diagnostics built into it?  Would there be copyright problems to
resolve before you could do this?

Tim. (shoppa at triumf.ca)

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