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Ilia Sharin 21751c0025 docs(amiga): complete AmigaOS 3.1/3.2 developer reference — 172 files across 17 sections

Comprehensive technical documentation covering:
- Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives
- Boot sequence: cold boot through startup-sequence
- Binary format: HUNK executable spec, relocation, debug info
- Linking & ABI: .fd files, LVO tables, register calling conventions
- Exec kernel: tasks, interrupts, memory, signals, semaphores
- AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting
- Graphics: planar bitmaps, Copper programming, HAM/EHB modes
- Intuition: screens, windows, IDCMP, BOOPSI
- Devices: trackdisk, SCSI, serial, timer, audio, keyboard
- Libraries: utility, expansion, IFFParse, locale, ARexx
- Networking: bsdsocket API, SANA-II, TCP/IP stack comparison
- Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging
- Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies
- CPU & MMU: 68040/060 emulation libs, PMMU, cache management
- Driver development: SANA-II, Picasso96/RTG, AHI audio

All files include breadcrumb navigation. No local paths or proprietary content.

2026-04-23 12:17:35 -04:00

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← Home · Boot Sequence

Cold Boot — Power-On to Kickstart

Overview

When the Amiga powers on or is reset (Ctrl-Amiga-Amiga), the 68000 CPU begins execution from the ROM. The boot process progresses from raw hardware init through to a fully running AmigaOS desktop in approximately 3–8 seconds.

Hardware Initialisation (Pre-ROM)

1. CPU Reset Vector

The 68000 reads two longwords from address $000000:

$000000: Initial SSP (Supervisor Stack Pointer)
$000004: Initial PC (Program Counter) → ROM entry point

On Amiga, these locations map to Kickstart ROM at $FC0000 (256 KB) or $F80000 (512 KB). The ROM image contains:

Word 0–1: SSP value (typically $000400)
Word 2–3: PC value → ROM entry point

2. ROM Checksum

First code executed: compute checksum of entire ROM. If it fails → red screen of death (solid red background, no further boot).

Checksum: simple 32-bit additive checksum of all ROM longwords.
Result must equal $FFFFFFFF (complement to zero).
The last longword of the ROM is the complement value.

3. Chip Register Reset

- Write $7FFF to INTENA ($DFF09A) — disable all interrupts
- Write $7FFF to INTREQ ($DFF09C) — clear all pending interrupts
- Write $7FFF to DMACON ($DFF096) — disable all DMA
- CIA chips: reset timer, serial, port registers

4. Memory Detection

The ROM probes for available memory:

1. Test Chip RAM at $000000 by writing test patterns
2. Size Chip RAM: 256 KB, 512 KB, 1 MB, or 2 MB
3. Probe for Fast RAM at $C00000 (Ranger), $200000 (Slow/Ranger)
4. Probe for Zorro II auto-config space at $E80000
5. Probe for 32-bit fast RAM at $07000000+ (Zorro III)

5. Display Diagnostic Colours

During boot, the background colour indicates progress:

Colour	Stage
Dark grey	ROM checksum passed
Light grey	Chip RAM sized
White	ExecBase initialised
Green flash	DOS boot starting
Red	ROM checksum fail
Yellow	Chip RAM test fail
Blue	Alert (Guru Meditation)

ROM Layout

256 KB ROM (Kickstart 1.x)

$FC0000–$FFFFFF  (256 KB)
  $FC0000: Reset vectors (SSP + PC)
  $FC0008: ROM header (version, checksum)
  ...
  $FC0020: First resident module (exec.library)
  ...
  $FFFFFC: Checksum complement word

512 KB ROM (Kickstart 2.0+)

$F80000–$FFFFFF  (512 KB)
  $F80000: Reset vectors
  $F80008: ROM header
  ...
  $F80020: exec.library resident tag
  ...
  $FFFFFC: Checksum complement

References

RKRM: Hardware Reference Manual — reset chapter

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