amiga-bootcamp/01_hardware/aga_a1200_a4000/gayle_ide_a1200.md

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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:

#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

#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.

/* 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