Recently, I have been successful in making A/UX boot and run stable on my vintage Macintosh emulator; Snow. A/UX was Apple’s version of UNIX that ran on the 68k-based series Macs. It required a Memory Management Unit to achieve process isolation; either the optional 68851 PMMU on the original 68020-based Macintosh II or the integrated MMU in the 68030- and 68040-based machines. It also required an FPU; making it only run on the higher end machines such as the Macintosh II series and later the Quadra, but the LC was out of luck. A/UX Penelope is a nice resource on A/UX compatibility info.

You can try A/UX 3.1.1 on the Macintosh IIx emulated by Snow in your browser on Infinite Mac.

Recently I had the chance to play with a newly archived A/UX 1.1 installation media set, courtesy of Dominic Sharp, whom I had been talking to on Tinker Different. Dominic obtained this set and wanted to archive it publicly, but wasn’t sure about the state of the disks. I’m not aware of any A/UX 1.1 software being publicly archived; the closest is a preinstalled image of 1.1.1, which didn’t work yet on Snow at the time. Dominic agreed to share the set with me so I could give it a try and fix Snow in the process.

The set consists of 34 floppy images, all 800K GCR. They came as raw flux images, which I first converted using Applesauce.

First, the proper emulated hardware had to be available. Snow emulates the machine, CPU, FPU and PMMU required, but only emulated the Macintosh Display Card 8-24, which I wasn’t sure was supported by A/UX 1.x, which is particularly picky about its video hardware. According to A/UX Penelope, the Macintosh II video card (“Toby”) is natively supported, so I first implemented this card as an additional option in Snow.

Then it was time to get to work with the installation. A/UX came with lovely very UNIX-y binders, which you definitely needed as the OS and installation aren’t exactly straight forward.

Luckily, that is archived on Bitsavers. Armed with my digital binders, I proceeded with the installation.

To start off the install, we begin with the “System setup and README” disk. We need to partition the disk, and then do something counter-intuitive: install System 6 on a Mac partition. This is because there’s a Mac application that kicks off the A/UX boot process: SASH; the A/UX standalone shell. This ‘pre-boot environment’ allows for launching an A/UX kernel and also some disk and recovery operations.

Partitioning is through the familiar HD SC Setup and can be pretty straightforward; the included HD SC Setup includes a template layout for A/UX.

And then, we can move on to install a pretty bare System 6 and afterwards copy the contents of the “SASH and utilities” disk to the new installation.

Now, it’s finally time to actually get into A/UX. This happens by booting off the “Floppy Launch” disk. This disk autostarts a SASH, launches an A/UX kernel and will then request the “Floppy Root” disk. This begins part 1 of the installation, which formats the A/UX partitions and copies a bootstrapping system into it.

At this point, I had to fix a Snow bug, which was causing the modifier keys to be stuck due to an invalid ADB Talk 2 implementation. Interestingly first time this is an issue; even A/UX 3.x was fine with it before.

diff --git a/core/src/mac/adb/keyboard.rs b/core/src/mac/adb/keyboard.rs
index 4e828fc..9edf31e 100644
--- a/core/src/mac/adb/keyboard.rs
+++ b/core/src/mac/adb/keyboard.rs
@@ -140,29 +146,34 @@ impl AdbDevice for AdbKeyboard {
                 response
             }
             2 => AdbDeviceResponse::from_iter(
-                AdbKeyboardReg2::default()
+                // The key/modifier bits of register 2 are ACTIVE LOW
+                AdbKeyboardReg2(0xFFFF)
+                    // LED state bits (0..2) are host-controlled and active-high
                     .with_led_numlock(self.keystate[SC_NUMLOCK as usize])
                     .with_led_capslock(self.capslock)
                     .with_led_scrolllock(self.keystate[SC_SCROLLOCK as usize])
-                    .with_numlock(self.keystate[SC_NUMLOCK as usize])
-                    .with_capslock(self.capslock)
-                    .with_scrolllock(self.keystate[SC_SCROLLOCK as usize])
-                    .with_cmd(self.keystate[SC_COMMAND as usize])
+                    .with_numlock(!self.keystate[SC_NUMLOCK as usize])
+                    .with_capslock(!self.capslock)
+                    .with_scrolllock(!self.keystate[SC_SCROLLOCK as usize])
+                    .with_cmd(!self.keystate[SC_COMMAND as usize])
                     .with_control(
-                        self.keystate[SC_LCTRL as usize] || self.keystate[SC_RCTRL as usize],
+                        !(self.keystate[SC_LCTRL as usize] || self.keystate[SC_RCTRL as usize]),
                     )
                     .with_option(
-                        self.keystate[SC_LOPTION as usize] || self.keystate[SC_ROPTION as usize],
+                        !(self.keystate[SC_LOPTION as usize] || self.keystate[SC_ROPTION as usize]),
                     )
-                    .with_delete(self.keystate[SC_DELETE as usize])
+                    .with_shift(
+                        !(self.keystate[SC_LSHIFT as usize] || self.keystate[SC_RSHIFT as usize]),
+                    )
+                    .with_delete(!self.keystate[SC_DELETE as usize])
                     .to_be_bytes(),
             ),
             3 => AdbDeviceResponse::from_iter(
                 AdbReg3::default()
                     .with_exceptional(true)
                     .with_srq(true)
-                    .with_address(Self::INITIAL_ADDRESS)
-                    .with_handler_id(2) // Apple Extended Keyboard M0115
+                    .with_address(self.address)
+                    .with_handler_id(self.handler_id)
                     .to_be_bytes(),
             ),
             _ => {

Then, we reboot to the hard disk where we launch SASH and A/UX for real for part 2 of the installation.

Here I hit another Snow bug: the kernel launch froze waiting for the NCR 5390’s ‘DMA end’ bit. Again; interestingly never was a problem before, even in newer A/UX versions.

diff --git a/core/src/mac/scsi/controller.rs b/core/src/mac/scsi/controller.rs
index 44f3959..a22ab29 100644
--- a/core/src/mac/scsi/controller.rs
+++ b/core/src/mac/scsi/controller.rs
@@ -771,10 +771,13 @@ impl BusMember<Address> for ScsiController {
             NcrReadReg::BSR => Some(
                 self.reg_bsr
                     .with_dma_req(self.get_drq())
-                    .with_dma_end(!matches!(
-                        self.busphase,
-                        ScsiBusPhase::DataIn | ScsiBusPhase::DataOut,
-                    ))
+                    .with_dma_end(
+                        self.reg_mr.dma_mode()
+                            && !matches!(
+                                self.busphase,
+                                ScsiBusPhase::DataIn | ScsiBusPhase::DataOut,
+                            ),
+                    )
                     .with_phase_match(self.phase_match())
                     .0,
             ),

Part 2 leads us through a whopping total of 26 “Installation disks” which contains the actual OS. As you can imagine, this took a while…

If you had a tape drive, you could opt for installing from tape, instead, saving you all that floppy swapping. Dominic also has this piece of history in his collection. If this tape ever gets archived, I’m definitely adding an emulated Apple 40SC tape drive to Snow so it is possible to do an installation from tape.

After the 26 disks, you reboot again, and there’s finally your final A/UX installation, booted by SASH on hard drive.

Now it was time for some peak UNIX gaming to celebrate. I’m happy Snow managed to get through this entire installation and A/UX 1.x now also runs smoothly.

You may be wondering if A/UX 1.x has any graphical interface. A/UX 3.x’s is pretty fancy and even allows you to run Macintosh applications through the ‘mac32’ emulation layer (I have ran Myst on A/UX 3.x) and even supports X11 applications.

Turns out, if you enter multi-user mode through init 2, you can run some graphical applications, called Toolbox applications (referring to the GUI ‘Toolbox’ in the Macintosh ROM) but there are only three such applications available..

Thanks again to Dominic for sharing the disks, which will eventually be publicly archived.