3 Jan
2020
3 Jan
'20
9:12 p.m.
I'm having a party on Saturday January 11 (and if any of you are in Tucson,
or want to come to Tucson for it, you're invited; email me for the address
and time).
Although the party is Elvis-themed, it's really about boardgaming and
classic videogaming.
So I kind of wanted to put a general-purpose Z-machine interpreter on my
PiDP-11, so that people could play Infocom (and community) games on a real
terminal.
Turns out there wasn't really one, so I ported the venerable ZIP (which I
have renamed "zterp" for obvious reasons) to 2.11BSD on the PDP-11, and I
also wrote a little utility I call "tmenu" to take a directory (and an
optional command applying to files in the directory) and make a numbered
menu, so that my guests who are not familiar with Actual Bourne Shell can
play games too.
These things are at:
https://github.com/athornton/pdp11-zterp
and
https://github.com/athornton/pdp11-tmenu/
Both are K&R C, and compile with the 2.11BSD system C compiler.
My biggest disappointment is that the memory map of Trinity, my favorite
Infocom game, is weird and even though it's only a V5 game, I can't
allocate enough memory to start it. Other than that, V5 and below seem to
work mostly fine; V8 is in theory supported but no game that I've tried has
little enough low memory that I can malloc() it using C on 2.11BSD.
Adam
4 Jan
4 Jan
1:59 a.m.
New subject: [PiDP-11] Some new text adventure stuff for 2.11BSD
Interesting. Trinity works fine under ZEMU.
So ZIP must be rather a hog...
V8 games that I've played under ZEMU:
BALLERINA
DREAMHOLDER
HEROINE
VIOLET
Johnny
On 2020-01-04 06:12, Adam Thornton wrote:
I'm having a party on Saturday January 11 (and if
any of you are in
Tucson, or want to come to Tucson for it, you're invited; email me for
the address and time).
Although the party is Elvis-themed, it's really about boardgaming and
classic videogaming.
So I kind of wanted to put a general-purpose Z-machine interpreter on my
PiDP-11, so that people could play Infocom (and community) games on a
real terminal.
Turns out there wasn't really one, so I ported the venerable ZIP (which
I have renamed "zterp" for obvious reasons) to 2.11BSD on the PDP-11,
and I also wrote a little utility I call "tmenu" to take a directory
(and an optional command applying to files in the directory) and make a
numbered menu, so that my guests who are not familiar with Actual Bourne
Shell can play games too.
These things are at:
https://github.com/athornton/pdp11-zterp
and
https://github.com/athornton/pdp11-tmenu/
Both are K&R C, and compile with the 2.11BSD system C compiler.
My biggest disappointment is that the memory map of Trinity, my favorite
Infocom game, is weird and even though it's only a V5 game, I can't
allocate enough memory to start it.? Other than that, V5 and below seem
to work mostly fine; V8 is in theory supported but no game that I've
tried has little enough low memory that I can malloc() it using C on
2.11BSD.
Adam
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--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
9:54 a.m.
On Sat, Jan 4, 2020 at 12:12 AM Adam Thornton via cctech
<cctech at classiccmp.org> wrote:
I'm having a party on Saturday January 11 (and if
any of you are in Tucson...
I'm a bit far off but it sounds cool.
So I kind of wanted to put a general-purpose Z-machine
interpreter on my
PiDP-11, so that people could play Infocom (and community) games on a real
terminal.
Fun!
Turns out there wasn't really one, so I ported the
venerable ZIP
https://github.com/athornton/pdp11-zterp
https://github.com/athornton/pdp11-tmenu/
Thanks for this.
My biggest disappointment is that the memory map of
Trinity, my favorite
Infocom game, is weird and even though it's only a V5 game, I can't
allocate enough memory to start it.
Is this just a 64K segment problem? Perhaps there needs to be some
examination and optimization of the impure and pure storage and
caching design?
One can play larger games with 128K of total RAM on microcomputers,
but most of those engines are written in assembler not C so the engine
is tightly coupled to the processor architecture.
-ethan
10:19 a.m.
So, it's _mostly_ a 64K problem. All z-machine games have, in the file
header, a "high memory" address above which it's safe to page data in and
out as needed, because it's all read-only. Trinity's header claims what
smells like an implausibly high value for a z4 game to me: 0xf771. There's
no way it needs _that_ close to the 64K limit for writable store. Its
"restart address" is 0x9310, though, which is also quite large, so maybe it
does do a lot more with RAM than most z-machine games?
The pure/impure and caching system is actually quite simple. Everything
below the "high memory" mark stays in RAM, everything above is divided into
512-byte pages which are paged in and out of the disk file as
necessary...so you need enough to cover dynamic memory, plus at least one
page, plus whatever your program requires. Cache replacement is simple
LRU. This works quite well in practice.
I'm already running with split I/D, which did help quite a lot, but not
enough to let me run something that claims to need all but 2K of the
potentially-writeable memory map.
ZEMU is much, MUCH tighter than ZIP, but of course it's in MACRO-11
assembly, not C-compiled-with-the-2.11BSD-C-Compiler, which isn't all that
tight a compiler by modern standards, and ZIP wasn't written to be
optimized for memory consumption anyway.
I tried compiling ZEMU with m11 on 2.11BSD, but there are zillions of
errors, and I certainly won't have time to figure it out (and write an
OS-dependent piece) by next Saturday. However, I may put ZEMU and a bunch
of games on the RSX-11 system on the PiDP-11 instead. But first I gotta
replace the spinner in my MAME cabinet.
Adam
On Sat, Jan 4, 2020 at 10:54 AM Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Sat, Jan 4, 2020 at 12:12 AM Adam Thornton via
cctech
<cctech at classiccmp.org> wrote:
I'm having a party on Saturday January 11
(and if any of you are in
Tucson...
I'm a bit far off but it sounds cool.
So I kind of wanted to put a general-purpose
Z-machine interpreter on my
PiDP-11, so that people could play Infocom (and community) games on a
real
terminal.
Fun!
Turns out there wasn't really one, so I
ported the venerable ZIP
https://github.com/athornton/pdp11-zterp
https://github.com/athornton/pdp11-tmenu/
Thanks for this.
My biggest disappointment is that the memory map
of Trinity, my favorite
Infocom game, is weird and even though it's only a V5 game, I can't
allocate enough memory to start it.
Is this just a 64K segment problem? Perhaps there needs to be some
examination and optimization of the impure and pure storage and
caching design?
One can play larger games with 128K of total RAM on microcomputers,
but most of those engines are written in assembler not C so the engine
is tightly coupled to the processor architecture.
-ethan
1813
days inactive
1813
days old
3 comments
3 participants
participants (3)
-
athornton＠gmail.com -
bqt＠softjar.se -
ethan.dicks＠gmail.com