[TUHS] 2.11BSD on a Z180 (was: merry christmas)

Nick Downing downing.nick at gmail.com
Sat Dec 31 20:27:48 AEST 2016

Yes, I am aware of the concept, I had used a similar emulator to run CP/M
binaries on MS-DOS, specifically Microsoft Macro-80, Link-80 and Basic-80
compiler. Yes I was doing cash registers that far back :) :) It is really
convenient having access to your host filesystem (compared with attaching a
simh formatted emulated tape image, tarring to/from it, and converting
to/rom simh format and plain binary as I did yesterday).

I hadn't seen apout but it is a good idea, I was toying with doing the same
thing by cross compiling the 2.11BSD kernel to create something like User
Mode Linux (but then adding user mode PDP-11 CPU emulation since it does
not make sense to compile x86-64 2.11BSD userspace executables even though
it is theoretically possible). I don't know how stable is the ABI between
Unix V7 and BSD or between BSD versions. I suspect it is very similar but
there would be differences in things like struct stat which are bound to
cause breakage. So I think it has to run the correct kernel to get the
correct ABI, and in turn that kernel has to have null or pass thru drivers
to access the host facilities. I do hope to get this working someday,
especially since a full cross compile of 2.11BSD includes the f77 stuff
which cannot reasonably be compiled on a modern system given the compiler
is not written in C, I think it is PDP-11 assembly.

For now I am trying to reduce the amount of stuff I need to change, so my
idea is to modify simh to allow switching between Z80 and PDP-11
instruction sets (I could use the PSW so that it can process an interrupt
or syscall in PDP-11 mode and transparently return to Z80 mode when it
restores the PSW) and then just convert little pieces at a time, I could
compile a Z80 hello world program and then link it against the PDP-11 C
library for instance. So this puts off having to deal with MMU or driver
issues till later on. I am looking at changing /lib/c1 and /bin/as to add a
.z80 directive and the z80 instruction set.

cheers, Nick

On 31/12/2016 5:19 PM, "Robert Swierczek" <rmswierczek at gmail.com> wrote:

> Have you looked into apout?  It is a user level simulator for Unix
> a.out binaries:
> https://github.com/DoctorWkt/unix-jun72/tree/master/tools/apout
> I have used it successfully for running some standalone binaries such
> as (~/v1/fs/root)/bin/as.
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