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.

01_hardware/aga_a1200_a4000/gayle_ide_a1200.md

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+[← Home](../../README.md) · [Hardware](../README.md) · [AGA](README.md)
+
+# Gayle — A1200 IDE & PCMCIA
+
+## Overview
+
+The A1200 uses a different revision of **Gayle** than the A600. The A1200 Gayle integrates:
+- **ATA/IDE interface** (for one hard drive + optional CD-ROM)
+- **PCMCIA Type II** slot (for modems, network cards, RAM cards)
+- **Interrupt routing** for both IDE and PCMCIA events
+
+The A1200 Gayle is at a different base address layout than the A600 Gayle, and the byte-lane mapping differs from the A4000 IDE interface.
+
+## Gayle ID
+
+Read the Gayle ID by toggling read access to the ID register:
+```c
+#define GAYLE_ID_A1200  0xDA8000   /* read 8 bits, shifts on each access */
+
+volatile UBYTE *gayle_id = (UBYTE *)0xDA8000;
+UBYTE id_byte = *gayle_id;   /* returns $D0 (A600) or $D1 (A1200) */
+```
+
+## IDE Register Map (A1200)
+
+The A1200 IDE registers are at `$DA0000`, but the byte lanes are **swapped** relative to standard AT/ATA convention — the 8-bit registers appear at odd byte offsets within each 4-byte window:
+
+| A1200 Address | ATA Register | RW |
+|---|---|---|
+| $DA0000 | Data (16-bit) | RW |
+| $DA0005 | Error (R) / Features (W) | RW |
+| $DA0009 | Sector Count | RW |
+| $DA000D | Sector Number (LBA 7:0) | RW |
+| $DA0011 | Cylinder Low (LBA 15:8) | RW |
+| $DA0015 | Cylinder High (LBA 23:16) | RW |
+| $DA0019 | Drive/Head select (LBA 27:24) | RW |
+| $DA001D | Status (R) / Command (W) | RW |
+| $DA101D | Alternate Status (R) / Device Control (W) | RW |
+
+> [!NOTE]
+> The odd byte offset is because Gayle maps ATA registers on the **odd byte lane** of the 16-bit Amiga bus. Accessing `$DA0000+1` is the first register, not `$DA0000`. Many IDE drivers compensate with an offset of +1 or use a byte-swapped struct.
+
+## Gayle Interrupt Register
+
+```
+$DA9000  GAYLE_INT_STATUS (read/write)
+$DA9004  GAYLE_INT_ENABLE
+```
+
+```c
+#define GAYLE_IRQ_IDE    (1<<7)  /* IDE interrupt pending */
+#define GAYLE_IRQ_CARD   (1<<6)  /* PCMCIA interrupt */
+#define GAYLE_IRQ_BVD1   (1<<5)
+#define GAYLE_IRQ_BVD2   (1<<4)
+#define GAYLE_IRQ_WP     (1<<3)  /* PCMCIA write protect */
+#define GAYLE_IRQ_CD     (1<<2)  /* PCMCIA card detect */
+```
+
+Gayle routes its interrupt to **CIA-A /FLG** pin → CIAA ICR `CIAICRF_FLG` → CPU IPL 6.
+
+Interrupt service routine must:
+1. Check `GAYLE_INT_STATUS` to identify source (IDE or PCMCIA)
+2. Clear the relevant bit by writing 0 to it
+3. If IDE: read the ATA status register to clear the IDE INTRQ
+
+## PCMCIA Interface (A1200)
+
+The A1200 PCMCIA slot is at:
+
+| Address | Content |
+|---|---|
+| $600000–$9FFFFF | PCMCIA attribute memory (card CIS) |
+| $A00000–$A3FFFF | PCMCIA common memory (data) |
+
+**Card detect sequence:**
+1. A card insertion triggers `GAYLE_IRQ_CD` (bit 2)
+2. Software reads CIS from attribute memory at $600000 to identify card type
+3. For ATA cards: configure card mode via PCMCIA CIS `CONFIG` tuple
+4. For network/modem cards: use the card's documented I/O mapping
+
+## AmigaOS IDE Access
+
+AmigaOS 3.1 includes `ata.device` (sometimes called `ide.device`) which drives the A1200 Gayle IDE internally. Applications never access Gayle registers directly — they go through dos.library → filesystem handler → ata.device.
+
+```c
+/* Standard path — no direct Gayle access needed: */
+BPTR fh = Open("DH0:myfile", MODE_NEWFILE);
+Write(fh, data, length);
+Close(fh);
+```
+
+## References
+
+- Commodore A1200 Technical Reference Manual — Gayle chapter (local archive)
+- NDK39: (no official Gayle header — community documented)
+- Amiga Hardware Reference (community supplement) — Gayle register map
+- `scsi.device` / `ata.device` Autodocs on ADCD 2.1