Quirks & Gotchas

Amix is a "quick and dirty" 1990–1992 SVR4 port ✅, and it shows: the kernel hard-codes SCSI IDs and a RAM ceiling, the bootstrap predates the 68040 and Zorro III, the clock breaks in 2000, and the userland is pre-POSIX. This page is the checklist of port-specific surprises — the things that are technically correct, technically broken, or just unexpected, that cost people hours before they realize "it's just Amix."

Each item is one line: what it is, the ✅/🟡 confidence tag carried from the research brief §12 (and §2/§9/§11), and a cross-link to the page that covers it in depth.

TL;DR checklist

#	Quirk	Tag	Deeper coverage
1	Tape must be ID 4 (hard-coded /dev/rmt/4h); disk ID 6 by convention — installer prompts for the target, but the ID is baked into device names, so don't change it post-install	✅/🟡	Hardware, Filesystems & disks
2	16 MB Fast RAM ceiling; more mis-maps the SCSI drive	✅	Hardware
3	No Zorro III — memory-mapping layer can't address it; unfixable	✅	Hardware, Zorro autoconfig
4	No 68040/68060 → the A4000 can't officially run Amix	✅	Hardware
5	Superkickstart dual-boot by holding the right mouse button at power-on	✅	Boot process
6	DNS resolution is OFF by default (/etc/hosts only)	✅/🟡	Networking
7	Y2K bugs: setclk %02d year + kernel date cap at 1999	✅/🟡	Versions, Patch ADF anatomy
8	SLIP is buggy — reboot between sessions; no PPP at all	🟡	Networking
9	X keymap is wrong: y/z swapped, / is SHIFT-8	🟡	X11 & desktop
10	amixpkg is widely reported broken (the wrapper, not pkgadd)	🟡	Install walkthrough
11	Clock drift via SCSI interaction	🟡	Networking
12	/bin/sh is pre-POSIX: no $(...), no grep -q	✅	Driver model, Writing a char driver
13	Enabling DNS adds ~3 min to every boot unless the boot-time ifconfigs (S69inet lo0, network-config aen0) use literal IPs instead of hostnames	✅	Networking, Networking on the LAN

The rest of this page expands each item.

Hardware & addressing quirks

1. SCSI IDs: tape fixed at 4, disk 6 by convention ✅/🟡

The tape drive must sit at ID 4 — the root-floppy install scripts hard-reference the literal /dev/rmt/4h and look nowhere else for it ✅. The hard disk is ID 6 by convention, not by kernel mandate: the installer prompts for the disk target and computes the boot partition from a $SCSI variable (BPART=/dev/dsk/c${SCSI}d0s${BOOTPART}), reserving only ID 4 for the tape — so Amix will install on a disk at another target 🟡. The catch is that the chosen ID is baked into the device names (c6d0s…) the installed system records in /etc/vfstab (the SVR4 mount table) and the boot partition, so you can't change the disk's SCSI ID after install without editing /etc/vfstab to match 🟡 (amix_21_root.adf analysis via tools/inspect-adf.sh; see hardware).

Consequence for emulation: attach your tape image at SCSI ID 4 (the installer looks only there) and your hardfile (RDB) at SCSI ID 6 — any target works for the disk, but 6 is the convention and saves you re-pointing /etc/vfstab later. See the mapping in the WinUAE setup and the FS-UAE setup. Disk geometry and partitioning are covered in filesystems & disks.

2. The 16 MB Fast RAM ceiling ✅

The kernel hard-codes a Fast RAM ceiling of 16 MB (minimum 4 MB) ✅. Going above 16 MB mis-maps the SCSI drive ✅ — the symptom is disk corruption / failure rather than an honest "too much RAM" error, which makes it a nasty trap. Set your emulator's Fast RAM to ≤ 16 MB. Background in hardware.

3. No Zorro III ✅

Amix's memory-mapping layer cannot address Zorro III space ✅. It is Zorro II only. Worse, the relevant kernel source was never shipped, so this can't be patched by the community ✅ — there is no community fix and there won't be one. Any expansion board you intend to use must present a Zorro II window; see Zorro autoconfig for how boards are discovered via the AUTOCONFIG / autocon() path, and hardware for the supported-board list.

4. No 68040/68060 — the A4000 is out ✅

The kernel predates the 68040 MMU ✅, so it runs only on a 68020 or 68030 with a real MMU plus a 68881/68882 FPU ✅. There is no soft-float and the MMU-less 68EC020/030 variants cannot run Amix ✅. Practical upshot: an A4000 cannot officially run Amix ✅. Targets are the A3000(UX) and the A2500UX. See hardware.

5. Superkickstart dual-boot via the right mouse button ✅

A3000UX machines ship a "Superkickstart 1.4" bootstrap ROM ✅. At power-on:

• Default (do nothing) → boot Amix from the SCSI disk.
• Hold the right mouse button at power-on → load an AmigaOS Kickstart instead.

So the "gotcha" is the inverse of what AmigaOS users expect: the machine boots Unix by default, and you reach AmigaOS only by holding a mouse button. Details in the boot process.

Networking quirks

6. DNS resolution is off by default ✅/🟡

Out of the box, name resolution uses /etc/hosts only — DNS is disabled ✅/🟡. To turn DNS on you relink the socket library and add config:

ln -f /usr/lib/libsockdns.so /usr/lib/libsocket.so   # swap in the DNS-capable socket lib
# then provide /etc/netconfig, start in.named (or point elsewhere), and write /etc/resolv.conf

Also note the routing gotcha: the default route needs an explicit metric — route add default <gw> 1 (the trailing 1 is required) ✅/🟡. Full procedure in networking.

8. SLIP is buggy; no PPP 🟡

SLIP works but is buggy: you must reboot between SLIP sessions 🟡, and there is no PPP at all 🟡. If you need a serial IP link, plan for a reboot cycle rather than re-dialing. See networking.

11. Clock drift via SCSI interaction 🟡

The system clock drifts, reportedly because of an interaction with SCSI activity 🟡. On a networked box you'll want a time-sync workaround; combined with the Y2K issues below, treat timekeeping as something to actively manage rather than trust. See networking.

13. Enabling DNS adds ~3 minutes to every boot ✅

Turning DNS on (quirk 6 above) drops a hidden tax on the boot path: with DNS enabled the box stalls ~3 minutes at The system is coming up. Please wait. on every boot ✅ (reproduced locally on Amix 2.1c under Amiberry). Stock Amix, with DNS off, does not.

The cause is two boot-time ifconfig calls that take hostnames, each forcing a gethostbyname() ✅:

• ifconfig lo0 localhost up — in /etc/rc2.d/S69inet
• ifconfig aen0 `uname -n` up -trailers — in /etc/inet/network-config

Both run before the default route is installed (route add default … happens later, in /etc/inet/rc.inet). With DNS on, gethostbyname() tries DNS first, but there is no route to the nameservers yet, so each lookup burns the full resolver retransmit schedule — ~90 s each, ~180 s total — before falling back to /etc/hosts ✅. With DNS off the same names resolve instantly from /etc/hosts, which is exactly why this trap appears only after you enable DNS.

This is independent of the /etc/domain weirdness ✅: a box with an already-empty /etc/domain still hangs the full 180 s — the domain-append bug and this no-route hang are two different problems.

Fix (boot 210 s → 29 s; runtime DNS unaffected): give both boot-time ifconfigs a literal IP so no resolver call happens before the network is up ✅:

# /etc/rc2.d/S69inet
-   /usr/sbin/ifconfig lo0 localhost up
+   /usr/sbin/ifconfig lo0 127.0.0.1 up
# /etc/inet/network-config
-   /usr/sbin/ifconfig aen0 `uname -n` up -trailers
+   /usr/sbin/ifconfig aen0 <this-host-static-ip> up -trailers

lo0 is always 127.0.0.1; aen0 uses the host's own static address (the one already in /etc/hosts). Configuring your own interface should never depend on a name service, so this is the correct design regardless — and DNS for clients/mail/etc. is untouched. Full procedure in networking and networking on the LAN.

Time & Y2K quirks

7. Y2K: setclk and the kernel's 1999 date cap ✅/🟡

Amix has two millennium problems ✅/🟡:

1. The setclk utility uses a %02d format for the year, so it mishandles dates ≥ 2000.
2. The kernel caps the date at 1999 — even the finishing-touches install step (amixadm) only accepts a date ≤ 1999 ✅.

These are community-patched ✅/🟡: applying the patch disk (which upgrades to 2.1p2a / kernel 2.1c) ships Y2K fixes, after which you run the corrected setclk ✅. See the patch mechanism in the patch ADF anatomy and the version timeline in versions.

X11 & desktop quirks

9. The X keymap is wrong 🟡

Under X11 the default keymap is mis-mapped 🟡:

• y and z are swapped.
• / is produced by SHIFT-8.

There are other X annoyances in the same family — xload crashes and the X11R4 server leaks memory 🟡. The modern RTG path (Xrtg / VA2000) sidesteps the old server but not the keymap mapping itself. Full X11 notes (mono tvtwm, A2410 color via TIGA, OpenLook font-path breakage on the R5 upgrade) are in X11 & desktop.

Userland & packaging quirks

10. amixpkg is flaky 🟡

The amixpkg wrapper around the SVR4 packaging tools is widely reported to be broken 🟡 — note this is the wrapper, not the underlying pkgadd/pkgmk/pkgtrans, which work. Despite the reputation, the official install path does drive it: the root-floppy installer runs amixpkg -i -m -d -r /mnt -y standard ✅. A related packaging gotcha: pkgproto omits symlinks 🟡. See the install walkthrough.

12. /bin/sh is pre-POSIX ✅

Amix's /bin/sh predates POSIX ✅. The two bites that catch driver authors and scripters:

• No command substitution with $(...) — you must use backticks `...`.
• No grep -q — redirect to /dev/null and test $? instead.

This was discovered the hard way porting the VA2000 driver: install scripts written with modern shell syntax silently misbehave ✅. The default interactive shell is ksh (with sh/csh/tcsh also present), but build and install scripts that run under /sbin/sh or /bin/sh must stay pre-POSIX ✅. See the driver model and writing a char driver for the driver-build implications, including the companion rule to rm -f stale objects before relinking the kernel.

See also

• Hardware — the machines, RAM ceiling, Zorro II, FPU/MMU requirements in full.
• Boot process — Superkickstart, the bootstrap, and on-disk layout.
• Networking — DNS, routing, SLIP, NFS, and clock notes.
• X11 & desktop — the X server, window managers, and keymap.
• Glossary — RDB, AUTOCONFIG, STREAMS, Superkickstart, and other terms used here.

Sources

• Research brief §12 (quirks checklist), with specifics pulled from §2 (hardware & limits), §9 (install flow + viper_kludge/Y2K), and §11 (networking, X11, userland).
• amix_21_root.adf analysis via tools/inspect-adf.sh — /dev/rmt/4h, BPART=/dev/dsk/c${SCSI}d0s${BOOTPART}, amixpkg -i -m -d -r /mnt -y standard.
• amix_21_patch.adf analysis via tools/inspect-adf.sh — patch-disk Y2K/inet fixes (→ 2.1p2a / kernel 2.1c).
• asokero/va2000-amix (pre-POSIX /bin/sh, no $(...), no grep -q; relink hygiene) — https://github.com/asokero/va2000-amix.
• Michael Ditto, Writing Amix Device Drivers, 1990 European Amiga Developer's Conference (driver/kernel model behind the SCSI-ID and /bin/sh notes).
• amigaunix.com DokuWiki — requirements, networking, x11, patch-disk, y2k-dst, tips-tricks, dual-boot pages (community-reported items): https://www.amigaunix.com/doku.php/home.
• BlitterStudio/amiberry issue #1376 and WinUAE/FS-UAE docs (emulation consequences of the SCSI IDs and RAM ceiling).
• The A4091-on-Amix project — networking investigation, 2026-06-07 (reproduced locally ✅): instrumented /etc/rc2 per-script timing on Amix 2.1c under Amiberry isolated S69inet at 180 s; boot 210 s → 29 s after switching the boot-time ifconfigs to literal IPs. Files: /etc/rc2.d/S69inet, /etc/inet/network-config, /etc/inet/rc.inet on the running system (quirk 13).