From: Adam Thornton <athornton@gmail.com>
To: Gabriel Diaz <gdiaz@qswarm.com>,
The Eunuchs Hysterical Society <tuhs@tuhs.org>
Subject: Re: [TUHS] Gaming on early Unix
Date: Fri, 6 Dec 2019 18:28:57 -0700 [thread overview]
Message-ID: <CAP2nic0uj6e37RMUfHqZJDc3PveBAFARPNpx81xQtJNYFT7Q=Q@mail.gmail.com> (raw)
In-Reply-To: <CAP2nic0S-rP4kq=sAyut-Qr5M5kyoHcCj=PZL07Xis=rv1uB3Q@mail.gmail.com>
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Well, OK, there's one other wrinkle. Building Frotz on 4.3BSD (or
whatever) on a VAX would be easy, because you have a 32-bit address space.
But the Z-machine can address 64Kwords (plus some trickiness for access
strings in high memory) so you'd have to actually implement a segmented
memory model or overlays or something to squeeze it into a PDP-11. Which
is obviously doable--after all, the Z-machine was designed to be
implemented on 8-bit micros!--but means that porting Frotz might be more
work than just writing a new interpreter, and supporting the later, larger
games (Infocom used the v5 format, which doubled the size and required 128K
even on 8-bit systems, and a lot of the post-Infocom community work--before
the community went to Glulx, which is a
32-bit-inspired-by-the-z-machine-virtual-machine-for-text-adventures--used
z8, which doubled the size again) is going to be harder.
Jimmy Maher has just been talking about the evolution of the Z-machine over
on filfre.net. It's well worth reading.
Adam
On Fri, Dec 6, 2019 at 6:22 PM Adam Thornton <athornton@gmail.com> wrote:
> There was not a Z-Machine interpreter for Unix machines, as far as I know,
> until the release of the ITF interpreter in the early 90s.
>
> However....
>
> Zork was developed under ITS (when it was "mainframe Zork" and an MIT
> student project), and the later Infocom games were developed under TOPS-20.
>
> As it happens, I've fairly recently ported the "Frotz" Z-Machine
> interpreter to TOPS-20. https://github.com/athornton/tops20-frotz and
> https://github.com/athornton/gnusto-frotz-tops20
>
> This was not all _that_ hard. KCC on TOPS-20 is an ANSI C compiler, so
> there were basically two classes of problems to solve.
>
> The first one is that the linker requires all symbols that are linked
> between modules to be six characters or shorter (and case is folded), so I
> wrote a transmogrifier (gnusto-frotz) to extract those symbols and create a
> mapping for them so that the object code would link.
>
> The second problem was that the Frotz source assumes 8-bit bytes and that
> your word length is a multiple of 8 bits. Since the Z-machine is a 16-bit
> virtual machine, that meant there was a whole lot of bit masking necessary
> in the opcodes and memory references in order to represent the Z-machine
> memory correctly within the TOPS-20 address space. That's done with stuff
> like:
>
>
> https://github.com/athornton/tops20-frotz/blob/0130a67fc44e0c7de1faa8f882cbc28faee76756/frotz.h#L488
>
> So the idea is, gnusto-frotz-tops20 is semantically equivalent to regular
> Frotz, but with macros changed so if you build it with -DWEIRD_WORDSIZE it
> would build on a 36-bit system. Then once you've modified the source, you
> run it through the transmogrifier (which really just generates a sed
> script) to get something that will _link_ on a 36-bit system.
>
> I have vague plans to port Frotz to ITS but the problem there is that the
> C compiler is pre-K&R rather than ANSI, so there's a lot of deprotoization
> work to be done, and _then_ I need to fix the things like += being =+ and
> so forth, and I think I have to chop another character off the symbols,
> which may mean I need smarter collision detection. So it's nontrivial.
>
> Maybe a good first step would be unprotoizing Frotz and getting it to
> build on v7 or so...
>
> Adam
>
> On Fri, Dec 6, 2019 at 3:52 AM Gabriel Diaz <gdiaz@qswarm.com> wrote:
>
>> Hello,
>>
>>
>> Source code has been published of some early games.
>>
>> Were those games playable on Unix machines at the time? What was your
>> favourite game?
>>
>>
>>
>> https://kryptonradio.com/2019/04/18/zork-source-code-presumed-lost-forever-has-been-uploaded-to-github/
>>
>>
>> Gabi
>>
>>
>>
>>
>>
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next prev parent reply other threads:[~2019-12-07 1:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-06 10:45 Gabriel Diaz
2019-12-06 11:01 ` Steve Nickolas
2019-12-06 14:23 ` A. P. Garcia
2019-12-06 14:48 ` A. P. Garcia
2019-12-08 7:48 ` arnold
2019-12-08 19:54 ` Clem Cole
2019-12-06 16:19 ` ron
2019-12-06 16:39 ` Richard Salz
2019-12-06 16:54 ` Dan Cross
2019-12-09 0:05 ` Steve Johnson
2019-12-09 0:35 ` Ken Thompson via TUHS
2019-12-09 0:46 ` Adam Thornton
2019-12-09 2:03 ` Rob Pike
2019-12-09 2:10 ` Ken Thompson via TUHS
2019-12-09 2:15 ` Rob Pike
2019-12-09 2:19 ` Ken Thompson via TUHS
2019-12-09 8:41 ` Gabriel Diaz
2019-12-09 11:17 ` Angelo Papenhoff
2019-12-09 8:40 ` Naveen Nathan
2019-12-06 17:24 ` Arthur Krewat
2019-12-06 17:58 ` Dr Iain Maoileoin
2019-12-06 22:12 ` ron
2019-12-07 0:04 ` Rob Pike
2019-12-07 1:22 ` Adam Thornton
2019-12-07 1:28 ` Adam Thornton [this message]
2019-12-10 0:30 Doug McIlroy
2019-12-10 5:08 ` Adam Thornton
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