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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.
139 lines
4.2 KiB
Markdown
139 lines
4.2 KiB
Markdown
[← Home](../../README.md) · [Hardware](../README.md)
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# Zorro Bus — Expansion Architecture
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## Overview
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The Amiga uses the **Zorro** expansion bus for add-on cards. There are two generations:
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- **Zorro II** — 16-bit, 24-bit addressing, 7 MHz, compatible with A2000/A3000/A4000
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- **Zorro III** — 32-bit, 32-bit addressing, up to 33 MHz burst, A3000/A4000 only
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Zorro uses **AutoConfig** — a standardised plug-and-play configuration protocol that predates PCI by several years.
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## Zorro II
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| Parameter | Value |
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|---|---|
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| Data bus | 16-bit |
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| Address bus | 24-bit |
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| Clock | 7.14 MHz (bus cycle ≈ 280 ns) |
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| Max transfer | ~5 MB/s (DMA) |
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| Address space | $A00000–$EFFFFF (I/O), $200000–$9FFFFF (RAM) |
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| Slots | 5 (A2000), 3 (A3000) |
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Zorro II cards appear in the 16 MB address space. RAM cards are configured into $200000–$9FFFFF. I/O cards use $A00000–$DEFFFF.
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## Zorro III
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| Parameter | Value |
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|---|---|
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| Data bus | 32-bit |
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| Address bus | 32-bit |
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| Clock | Up to 33 MHz burst |
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| Max transfer | ~40 MB/s (DMA) |
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| Address space | $01000000 and above |
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| Slots | 4 (A3000), 5 (A4000) |
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Zorro III extends into the 32-bit address space, allowing large RAM cards (32–128 MB) and fast peripherals. Requires a 32-bit CPU (68030+) and OS support.
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## AutoConfig Protocol
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AutoConfig allows the OS to discover and configure cards without jumpers:
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```mermaid
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sequenceDiagram
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participant OS as AmigaOS (expansion.library)
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participant Card as Zorro Card
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OS->>Card: Read $E80000 (config space)
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Card-->>OS: Manufacturer ID (16-bit)
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OS->>Card: Read $E80002
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Card-->>OS: Product ID, flags
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OS->>Card: Read board size, type
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OS->>OS: AllocAbs() / ConfigBoard()
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OS->>Card: Write base address
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Card-->>OS: Card configured, moves off $E80000
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```
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**Key AutoConfig registers** (read from $E80000–$E8007F before configuration):
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| Offset | Content |
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|---|---|
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| $00 | er_Type (board type: RAM/IO, Zorro II/III) |
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| $02 | er_Product (product ID) |
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| $04 | er_Flags |
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| $06 | er_Reserved03 |
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| $08–$0A | er_Manufacturer (16-bit) |
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| $0C–$0F | er_SerialNumber |
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| $10–$11 | er_InitDiagVec (diagnostic ROM vector) |
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**Board types** (`er_Type` bits):
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```c
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#define ERT_TYPEMASK 0xC0
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#define ERT_ZORROII 0xC0 /* Zorro II card */
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#define ERT_ZORROIII 0x80 /* Zorro III card */
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#define ERTB_MEMLIST 5 /* board is RAM, add to free list */
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#define ERTB_DIAGVALID 4 /* DiagArea ROM is valid */
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#define ERTB_CHAINEDCONFIG 3 /* more boards to configure */
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```
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## expansion.library
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AmigaOS provides `expansion.library` to manage Zorro configuration:
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```c
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#include <libraries/expansion.h>
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#include <clib/expansion_protos.h>
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/* Find a configured board by manufacturer/product */
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struct ConfigDev *cd = NULL;
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while ((cd = FindConfigDev(cd, MANUF_ID, PROD_ID)) != NULL) {
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APTR base = cd->cd_BoardAddr;
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ULONG size = cd->cd_BoardSize;
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/* use board at base */
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}
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```
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**Key structures:**
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```c
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struct ConfigDev {
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struct Node cd_Node;
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UBYTE cd_Flags;
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UBYTE cd_Pad;
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struct ExpansionRom cd_Rom; /* copy of autoconfig ROM area */
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APTR cd_BoardAddr; /* configured base address */
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ULONG cd_BoardSize;
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UWORD cd_SlotAddr;
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UWORD cd_SlotSize;
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APTR cd_Driver;
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struct ConfigDev *cd_NextCD;
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ULONG cd_Unused[4];
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};
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```
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## DiagArea — Card ROM
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Cards with `ERTB_DIAGVALID` have a small ROM (DiagArea) that the OS calls during boot:
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```c
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struct DiagArea {
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UBYTE da_Config; /* flags */
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UBYTE da_Flags;
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UWORD da_Size;
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UWORD da_DiagPoint; /* offset to diagnostic code */
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UWORD da_BootPoint; /* offset to boot code */
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UWORD da_Name; /* offset to name string */
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UWORD da_Reserved01;
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UWORD da_Reserved02;
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};
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```
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The boot vector is called by `ConfigChain()` during the early boot sequence — this is how SCSI controllers install their filesystem handlers.
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## References
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- NDK39: `libraries/expansion.h`, `libraries/configregs.h`, `libraries/configvars.h`
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- ADCD 2.1 Autodocs: `expansion` — http://amigadev.elowar.com/read/ADCD_2.1/Includes_and_Autodocs_3._guide/node025B.html
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- *Amiga Hardware Reference Manual* 3rd ed. — AutoConfig chapter
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- Dave Haynie's Zorro III specification documents
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