[TUHS] Disassemblers

[Clem Cole]

On Sat, Jun 19, 2021 at 12:33 PM Henry Bent <henry.r.bent at gmail.com> wrote:

> Wait, so it was easier to write an emulator for a PDP-10 binary than it
> would have been to port BLISS to the PDP-11?  Given the different word
> sizes I would not have expected that.
>
BLISS-11 was (way) too big to run in the 64K address of the PDP-11 (even
separated I/D).  Originally, it was a PDP-10 cross compiler and later moved
to the Vax.   It generated much better code than the original Ritchie or
later Johnson compilers.   The code generator/optimizer was famous
(literally the book on code optimization was written about it, called of
course: "The Design of an Optimizing Compiler"
<https://www.amazon.com/Design-Optimizing-Compiler-William-Allan/dp/0444001581>
by
Wulf and some of his students [ISBN 0444001581] - *a.k.a.* 'The Green Book'
worth reading BTW.

Later on, DEC's TLG tried at least twice that I know of to make it
self-hosting but gave up. Long story (and definitely a different thread) if
DEC has not screwed up the marketing of BLISS, I suspect it might have
given C a run for the money.  But BLISS *vs*. C is a great example of
Cole's law that *Simple Economics always beats Sophisticated Architecture*
[and using Christensen's 'disruptive theory -- it gets better and supplants
the incombent].

Anyway, the compiler/code generator/linker for DEC Fortran-IV for RT-11,
RSX, and DOS-11 was written in BLISS-11.  So for CU to retarget it for V6
they needed a PDP-10, which they did not have.  So they wrote a simulator.
I remember when they gave a talk about it at Usenix, somebody asked them
how well Tenex ran on it.




> Did they have a cover sheet or something equivalent that they came with?
> I'm having trouble imagining dealing with that much unindexed data on an
> early system.
>
Not to my knowledge.  Two things that I believe we need to do for the TUHS
archives to be even more meaningful is 1.) decode them from tp/ar -- even
if you read the tape, they are packed together in v5/v6 ar files which are
PDP-11 binary.  2.) Create an index of what is there.

I've thought about both things but have way too much on my plate to do it
myself.

> Fascinating.  Thank you as always for the insight.
>
Most welcome.
Clem
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