alt.hn

4/11/2026 at 3:39:19 PM

Advanced Mac Substitute is an API-level reimplementation of 1980s-era Mac OS

 https://www.v68k.org/advanced-mac-substitute/

by zdw

4/12/2026 at 1:48:53 AM

This is super cool. I love that look. Something about classic black & white macos has a timeless "alternative timeline" L'Air de Panache aesthetic that to me says credibility and stability. Maybe it's the memory of the rows of Macintosh SE or Plus, those solid little upright beige bricks, in the computer room at my elementary school.

I made a MacOS system 7 web desktop UI with real web browsing: https://win9-5.com/macos/

A re-imagining.

by keepamovin

4/12/2026 at 2:26:59 AM

Oh wow. Once I saw the smiling machine and empty progress bar, I went straight to NoScript and enabled your domain without a moment's hesitation — highly unusual for me. It's charming! I laughed out loud when I saw your screen-saver.

It's familiar and alien at the same time, like I'm seeing an alternate universe.

I made my own web-based Mac simulator some time ago: https://www.metamage.com/apps/maxim/

It was a way to become more familiar with CSS and JS (and indulge my classic Mac OS nostalgia), but my biggest takeaway was that the web wasn't a foundation I wanted to build complex structures on, and indirectly helped spur me to create Advanced Mac Substitute.

by jjuran

4/11/2026 at 7:32:43 PM

This is pretty neat. I have been spending the past few months adding an ARM64 JIT to Basilisk II (https://github.com/rcarmo/macemu) and totally appreciate what's involved (I'm currently stuck patching a Quadra ROM to bypass NuBus hardware detection...)

Will definitely give it a try, since I would _love_ to have a Classic Mac environment with some modern creature comforts (like file sharing) in tiny machines.

by rcarmo

4/11/2026 at 6:48:58 PM

I am amazed that 1980's software works on binary API compatibility rather than relying on API quirks like timing, memory alignment quirks, memory layout from specific allocator behaviour, etc.

It only takes one unintentional reliance on an implementation detail to make an application not run on another OS implementation...

by londons_explore

4/11/2026 at 8:25:26 PM

The Mac classic was about as pure as you could get from an architectural point of view.

A 1 bit framebuffer and a CPU gets you most of what the machine can do.

Most of the quirk abuse of 8-bit machines came from features that were provided with limitations. Sprites, but only 8 of them, colours but only 2 in any 8x8 cell. Multicolour but only in one of two palettes and you'll hate both.

Almost all of the hacks were to get around the limitations of the features.

I don't know if the decision apple made was specifically with future machines in mind. It certainly would have been a headache to make new machines 5 generations down the track if the first one had player missile graphics.

by Lerc

4/11/2026 at 7:14:13 PM

There were plenty of apps that relied on implementation quirks.

by wmf

4/11/2026 at 8:42:20 PM

They mostly relied on OS/Toolbox implementation quirks though, not hardware implementation quirks, because applications that relied on the latter wouldn’t run on the Macintosh XL and that mattered to certain market segments. (Like some people using spreadsheets, who were willing to trade CPU speed for screen size.) Similarly anything that tried to use floppy copy protection tricks wouldn’t work due to the different system design, so that wasn’t common among applications.

So even things that wrote directly to the framebuffer would ask the OS for the address and bounds rather than hardcode them, copy protection would be implemented using license keys (crypto/hashes, not dongles) rather than weird track layouts on floppies, etc. It led to good enough forward compatibility that the substantial architectural changes in the Macintosh II were possible, and things just improved from there.

by eschaton

4/11/2026 at 8:49:56 PM

Eh, there were plenty of games that were coded for a particular clock speed, and then once the SE came out, had an update that included a software version of a turbo button, let you select which of two speeds to run at. They run FAST on an SE/30 or Mac II and unusably fast on anything newer.

by icodestuff

4/11/2026 at 8:59:44 PM

I didn’t encounter too many of those back in the day, I think because there was the VBL task mechanism for synchronizing with screen refresh that made it easy to avoid using instruction loops for timing.

Much more common in my experience was the assumption that the framebuffer was 1-bit, but such games would still run on my IIci if I switched to black & white—they’d just use the upper left 3/4 of the screen since they still paid proper attention to the bytes-per-row in its GrafPort.

Could be that by the time I was using a Mac II though that all the games that didn’t meet that minimum bar had already been weeded out.

by eschaton

4/11/2026 at 10:27:26 PM

Yeah, there were a bunch of floppy games which only ran on an original Mac or maybe a Plus. No go with even my Mac SE.

by flomo

4/12/2026 at 4:38:24 AM

Indeed, even ones from companies as big as Microsoft!

There is a story in Writing Solid Code by Steve Maguire [1] where Apple asked Microsoft to fix hacks in its Mac apps that didn't conform to the developer docs in Inside Macintosh because such workarounds were required when the apps were first developed alongside the original Macintoshes. However, Microsoft's workarounds would be broken by a major System Software update under development at Apple, which naturally wanted to avoid having to permanently add back the implementation bugs and quirks that the workarounds either relied on or were meant to avoid.

As Maguire told it, removing one such workaround in Microsoft Excel was hotly debated by the Excel team because it was in a hot-path 68k assembly function and rewriting the code to remove it would add 12 CPU cycles to the function runtime. The debate was eventually resolved by one developer who ran Excel's "3-hour torture test" and counted how many times the function in question was called. The total: about 76,000 times, so 12 more cycles each time would be about 910,000 cycles total... which on the Macintosh 128k's ~7 MHz 68000 CPU would be about 0.15 seconds added to a 3-hour test run. With the slowdown from removing the workaround thus proven to be utterly trivial, it was indeed removed.

[1] https://openlibrary.org/books/OL1407270M/Writing_solid_code - page 136, heading "Don't Overestimate the Cost"

by hyperrail

4/11/2026 at 8:43:39 PM

Out of curiosity, what app are you thinking of? Of all of types of software used with classic Mac OS (INITs, CDEVs, FKEYs, Desk Accessories, Drivers, etc.), apps would be the least likely to rely on implemention quirks.

by CharlesW

4/11/2026 at 11:34:38 PM

Macintosh Common Lisp - at least the versions floating around Mac Garden and such - seems to refuse to run on anything besides accurate emulators and real hardware.

by wk_end

4/12/2026 at 1:39:15 AM

Very cool! This reminds me of ARDI Executor [1] - a piece of (discontinued) commercial software first released in 1990 that took the same API-level reimplementation approach used here. And it did so jaw-droppingly fast considering that it was running on 90s PC hardware. As a little kid using it to play a few Mac games on my Windows PC, it was genuinely inspiring to me to see that this was possible at a time when I was first learning how to code. :) Great to see something with a more modern implementation doing this as well!

It was discontinued in 2005, but the developers subsequently open sourced it and put the code on GitHub a couple years later. [2]

[1] https://en.wikipedia.org/wiki/Executor_(software)

[2] https://github.com/ctm/executor

Bonus: One of the engineers from ARDI, the startup that created Executor, was very briefly featured in Bob Cringely's 1996 documentary Triumph of the Nerds talking about the lifestyle of working at prototypical mid-90s Silicon Valley startup.

by epenn

4/11/2026 at 5:27:12 PM

I can't imagine how fast this is compared to the original hardware that ran it. I remember using a Mac 512k with a single floppy drive (no hard drive support) and doing the insert-floppy-dance. Computers were far more mechanical then.

It would be fun to have a "slow it down" feature that also has the various floppy read/write noises paired with it. Bonus points for different generations of hardware and having the OG HD noises to pair with those too!

by imoverclocked

4/11/2026 at 6:04:06 PM

There was a show HN retro HW project somewhat recently that included sound emulation on board. Maybe that author is reading this, but their sound emulation was probably my favorite part (not to disregard the actual hard parts! I just found it charming)

by drzaiusx11

4/12/2026 at 2:16:35 AM

Just tried out this apple II emulator that’s close to what you’re describing, but for Apple II https://www.virtualii.com/ . Has floppy sounds as well as speed settings.

by steve-atx-7600

4/11/2026 at 7:31:34 PM

"Fond" memories of playing King's Quest IV as a little kid on my parents' Apple IIe. You had to swap in a new 5.25" floppy almost every time you walked to another screen. I was fascinated by the game but my god was it tedious to constantly flip and swap the disks around. Google says it came on 8 double sided disks, I could have sworn it was a couple dozen.

by jdwithit

4/11/2026 at 7:59:10 PM

The game I played for hours on the Apple ][+ was "FantasyLand 2041". It came on six double sided disks, and I was bummed to find out after quite a lot of game time that disk six was corrupted. I then found out many years later that it wasn't corrupted, the game wasn't ever finished. I then further discovered that John Bell, who produced that and other popular games (Sand of Mars, Beneath the Pyramids, House of Usher), is utterly batty and has written a few "the government is hiding UFOs from us" books.

by technothrasher

4/11/2026 at 5:17:55 PM

I'd like to see something like Carbon for old apps so that they boot in modern window frames (without the missing Tahoe corners) and can save to files.

by hyperhello

4/11/2026 at 8:50:06 PM

Advanced Mac Substitute stores documents and preference files in sandboxed host directories.

For example, check out the MacPaint demo:

https://www.v68k.org/advanced-mac-substitute/demo/MacPaint-A...

If you were to double-click the Hello document in macOS' Finder, it would launch and open in MacPaint.app.

by jjuran

4/11/2026 at 7:48:32 PM

This is exactly the sort of project that can serve as the basis for such a system.

by eschaton

4/11/2026 at 7:29:38 PM

So has this beaten MACE to the finish line? Or are the goals different? https://mace.home.blog

by msephton

4/11/2026 at 5:11:30 PM

But will it run Dark Castle??

Many hours were wasted on that game.

by shermantanktop

4/11/2026 at 7:23:34 PM

Hell, I’d go straight for Beyond Dark Castle… it really took the series to a whole different level.

by Chazprime

4/11/2026 at 4:51:52 PM

Wine for classic Mac OS? Amazing. Well done.

by davidfstr

4/11/2026 at 7:19:55 PM

Sounds like Wine + FEX

by bsimpson

4/11/2026 at 4:30:45 PM

related discussion https://news.ycombinator.com/item?id=40338443

by homarp

4/12/2026 at 7:29:23 AM

Funny you should bring up MacRelix — the very first front end for Advanced Mac Substitute was built in it.

by jjuran

4/11/2026 at 8:16:11 PM

Very cool. If it's built on SDL2, it should be straightforward to make it run in the browser via Emscripten, right?

by andai

4/11/2026 at 9:28:37 PM

Advanced Mac Substitute uses a factored approach. 68K emulation happens in the back end, which is a collection of processes connected by Unix-domain sockets, portable to basically any POSIX system.

The front end deals with displaying graphics and forwarding user input to the back end. Working front ends include SDL2 (by a contributor), X11, Linux fbdev, VNC, and five different macOS APIs (Cocoa/OpenGL, CGL, AGL, Quartz, and QuickDraw).

The front and back ends communicate using FIFOs and shared memory. I'm aware that certain platforms will require refactoring all of this to run in a single process. If Emscripten is one of them, then it won't be as simple as you suggest.

In any case, if I were the one doing the port, I might write a bare-bones front end just for this purpose, possibly using the fbdev one as a starting point.

by jjuran

4/12/2026 at 10:04:40 AM

As far as I can tell, the simplest solution would be to run the whole thing in a PC emulator. Simultaneously elegant, and deeply unsatisfying ;)

by andai

4/11/2026 at 11:03:12 PM

Efforts like this could be a nice way to get old apps to run "natively" on current hardware, as there are a ton of them out there which are perfectly good for work, but which cannot run today.

by flenserboy

4/11/2026 at 11:09:33 PM

I'd be glad of being able to run Macromedia Freehand/MX thus.

by WillAdams

4/11/2026 at 5:27:43 PM

This triggered flashbacks. I'm not sure if I'm remembering correctly, but I think we sometimes also used used Pascal, and it was optional for some toolboxes. It's been a long time though so I could be mistaken. That might have been pre-Mac? But good times, though. Boy, is the world a different place.

by Batbird

4/11/2026 at 6:36:58 PM

The original Mac system software was written in Pascal and most Mac toolbox calls took Pascal-style (prefixed by length) rather than C-style (terminated with null character) strings. But you could write application code in either language keeping this caveat in mind.

by DavidSJ

4/11/2026 at 8:02:44 PM

It was actually mostly written in assembly, but used Pascal calling conventions and structure layouts since that was expected to be the primary language for application developers. As it had been for Lisa, as it was for “large” applications on Apple II, and as was the case for much of the rest of the microcomputer and minicomputer industry and even the nascent workstation industry (eg Apollo).

It was the Lisa system software that was mostly implemented in Pascal and some blamed this for its largeness and its performance. Compilers and linkers weren’t great back then; most compiler code generation was pretty rigid, and most linkers didn’t even coalesce identical string literals across compilation unit boundaries!

Lisa Workshop C introduced the “pascal” keyword for function declarations and definitions to indicate they used Pascal calling conventions, and otherwise followed Lisa Pascal structure layout rules, so as to minimize the overhead of interoperating with the OS. (I’m not sure whether it introduced the “\p” Pascal string literal convention too or if that came later with Stanford or THINK Lightspeed C.)

by eschaton

4/12/2026 at 3:44:02 AM

That brings back the memories. I had a copy of Lightspeed C for the Mac in college.

In the workstation world, most companies used C and not Pascal. Apollo was different in that regard as their operating system, Domain, was unique to themselves, while most of the other workstation companies (Sun, HP, DEC, and IBM) were using Unix variants of some time (either BSD-based or System V-based in most cases). Apollo Domain was written in Pascal and was definitely not Unix-based. It had many unique and interesting features. In particular it had very sophisticated authentication and file sharing capabilities. A user could log in on any machine that was part of the domain (hence the name) and the user’s complete file system would be made available over the network on that hardware. Every system on the network shared a domain-level file system which removed the need for many Unix solutions like NFS. I had just accepted a job offer out of college from HP’s workstation division when HP bought Apollo. By the time I started, a couple months later, I was part of the HP side of the Apollo Systems Division.

by drob518

4/11/2026 at 11:13:52 PM

A good example of this dichotomy is the Puzzle Desk Accessory --- originally written in Pascal (as an example of making a DA thus), it was too large to include on a 400KB micro-floppy disk, so was re-written in assembly language going from 6K Bytes to 600 Bytes:

https://www.folklore.org/Puzzle.html

by WillAdams

4/11/2026 at 4:25:39 PM

This is quite the feat. I’d love to know more about the process to make this, the motivation, how much time was spent, etc.

by azinman2

4/11/2026 at 4:54:58 PM

I'm guessing they reimplemented the toolbox at the TRAP level (most MacOS calls at the time were accessed through the 68K TRAP instruction).

So, rather than emulating hardware to run native ROMs, they "simply" reimplemented the ROMs.

A friend of mine did this at another level. He basically rewrote the bulk of the toolbox as a C library so that the company, who had a Mac application, could port it to run on a PC, while sharing the source code.

This was before Windows, and it worked! Launched it from DOS, takes over the entire screen. He didn't copy the Mac look and feel. Instead he used OpenLook for his gadgets and what not (since it was, you know, "open").

But he rewrote the bulk of it: QuickDraw, Event Manager, Memory Manager, Window Manager, etc. Just ate it like an elephant. I don't think his regions were as clever as the Mac. Pretty sure he just stuck with rectangles.

by whartung

4/11/2026 at 8:28:38 PM

Correction: 68K Mac OS calls were A-line traps — in other words, they had opcodes of the form `$Axxx`. To the processor, they're unimplemented instructions that each take an exception through the same vector. The exception handler is the Mac OS trap dispatcher.

`TRAP` is a different instruction, with opcodes `$4E4x`. Each one gets its own exception vector.

It's not just trap calls, though — sometimes applications write directly to the sound buffer or use hardware page flipping.

by jjuran

4/11/2026 at 9:26:37 PM

As I recall MacOS system calls were done through invalid instructions which would cause the CPU to "trap" (raise an interrupt). Giving rise to the question Mac extension writers asked of each other: "How many traps did you patch?"

by bitwize

4/12/2026 at 4:57:29 AM

You want to talk trap patches? Your Mac's INITs have minimal trap patches, touch the Toolbox in boring places like SysBeep() and GetNextEvent(). The Developator's Mac has big, tricky INITs with trap patches that hook into half of the Device Manager.[1] The Developator is in touch with the metal, starts like a warm boot off the ROM reset vector, stops on an NMI.

[1] See https://www.macrelics.com/legacynth/

by jjuran

4/11/2026 at 9:51:40 PM

My earliest recollection of what motivated me is a desire to resurrect The Fool's Errand.

The irony is not lost on me. :-)

by jjuran

4/12/2026 at 2:51:36 AM

Hey, I’ve been thinking about building a genesis emulator to play Revenge of Shinobi. Never thought about trying to replace the genesis rom.. let’s get the game working first :)

by azinman2

4/12/2026 at 2:57:10 AM

A Genesis has to start somewhere. ;-)

by jjuran

4/12/2026 at 3:47:43 AM

Wow! Who is the madman that created this?

by msie

4/11/2026 at 5:21:22 PM 

   make ams-vnc
   ./build.pl -i exhibit graft skif minivx xv68k freemountd listen vnc-interact

   ...

   Daemon starting up... done.
   T=0.037s  ERROR:    OpenDF is unimplemented
Hm, doesn't seem to work. Let's try the X11 version:

   make ams-x11
   ./build.pl -i exhibit graft skif minivx xv68k freemountd interact-x11

   ...

   T=0.275s  ERROR:    OpenDF is unimplemented
Nope, it seems to be missing something. OpenDF? All I find is this: https://github.com/PrjEnt/OpenDF, a long-abandoned project which seems to be a more compact version of another abandoned thing.

by hagbard_c

4/11/2026 at 5:56:40 PM

I think they mean FSpOpenDF (https://dev.os9.ca/techpubs/mac/Files/Files-53.html#HEADING5...), a (relatively) late addition to the Mac API.

by Someone

4/11/2026 at 7:48:04 PM

The FSSpec calls added in System 7 are mostly new interfaces to existing File Manager functionality. There's an actual high-level `OpenDF()` call, which is like `FSOpen()` except that it won't try to open a driver when the name begins with `.`.

Some applications call `OpenDF()` without checking its availability, but fall back to `FSOpen()` or equivalent if `OpenDF()` returns `paramErr`, which is what the parent is witnessing. See `68k/modules/ams-fs/Files.cc` in the `metamage_1` repo.

If the error message is confusing people, maybe it's time to implement `OpenDF()` for real.

by jjuran

4/11/2026 at 10:25:00 PM

I had that error with Nethack 3.6.7 for m68k.

by anthk

4/12/2026 at 5:07:36 AM

It's not you; it's me. My implementation of LoadScrap() (which is called at startup) is calling FSOpen(), and it turns out the glue code for that tries OpenDF() before falling back to PBOpen(). TIL.

The call is coming from within the OS!

by jjuran

4/11/2026 at 9:38:06 PM

That, or add this information to the error message: OpenDF not implemented, falling back to FSOpen

by hagbard_c

4/11/2026 at 8:04:53 PM

Ah, yes, the two front ends I haven't touched in years. This should be fun. :-)

You clipped the part that said "Starting VNC server on 127.0.0.1:5900". Did you try connecting a VNC client?

by jjuran

4/11/2026 at 5:40:34 PM

OpenDF is a MacOS toolbox call (which is apparently not implemented)

by ksherlock

4/11/2026 at 6:55:59 PM

Strange it errors out on given that I assume the thing does run elsewhere. The X11 version sometimes shows the opening screen but any attempt at interaction leads to the mentioned error. The VLC version shows the error directly.

by hagbard_c

4/11/2026 at 8:07:43 PM

Any interaction with the Welcome application terminates it. Try setting AMS_APPNAME=Tic-tac-toe in the environment, or AMS_APPNAME="Nyanochrome Cat".

by jjuran

4/11/2026 at 8:26:47 PM

Yes, that works, the tic-tac-toe thing appears and remains even though the error message regarding OpenDF is shown. In other words that error message can be ignored, at least as long as whatever is in AMS_APPNAME does not require whatever OpenDF provides.

by hagbard_c

4/11/2026 at 10:23:04 PM

Executor from autc04 was fine until I tried to open Nethack 3.6.7 for m68k Macs. It crashed, but it was a fun exercise.

AMS might work better, but it's a pain to setup.

by anthk