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docs: minor updates to zorro_bus, game_reversing, expansion

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Ilia Sharin 2026-05-12 22:04:26 -04:00
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01_hardware/common/zorro_bus.md
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@ -37,99 +37,11 @@ Zorro II cards appear in the 16 MB address space. RAM cards are configured into
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.
## AutoConfig Protocol
## AutoConfig
AutoConfig allows the OS to discover and configure cards without jumpers:
Zorro uses **AutoConfig** — a hardware plug-and-play protocol that lets the OS discover, size, and map expansion boards at boot without jumpers. Each board presents a 256-byte ROM at the configuration address (`$E80000` for Zorro II, `$FF000000` for Zorro III) containing its manufacturer ID, product code, size, and type. The OS walks the `/CFGIN`/`/CFGOUT` daisy chain, reads each ROM, assigns a base address, and tells the board to relocate.
```mermaid
sequenceDiagram
participant OS as AmigaOS (expansion.library)
participant Card as Zorro Card
OS->>Card: Read $E80000 (config space)
Card-->>OS: Manufacturer ID (16-bit)
OS->>Card: Read $E80002
Card-->>OS: Product ID, flags
OS->>Card: Read board size, type
OS->>OS: AllocAbs() / ConfigBoard()
OS->>Card: Write base address
Card-->>OS: Card configured, moves off $E80000
```
**Key AutoConfig registers** (read from $E80000–$E8007F before configuration):
| Offset | Content |
|---|---|
| $00 | er_Type (board type: RAM/IO, Zorro II/III) |
| $02 | er_Product (product ID) |
| $04 | er_Flags |
| $06 | er_Reserved03 |
| $08–$0A | er_Manufacturer (16-bit) |
| $0C–$0F | er_SerialNumber |
| $10–$11 | er_InitDiagVec (diagnostic ROM vector) |
**Board types** (`er_Type` bits):
```c
#define ERT_TYPEMASK 0xC0
#define ERT_ZORROII 0xC0 /* Zorro II card */
#define ERT_ZORROIII 0x80 /* Zorro III card */
#define ERTB_MEMLIST 5 /* board is RAM, add to free list */
#define ERTB_DIAGVALID 4 /* DiagArea ROM is valid */
#define ERTB_CHAINEDCONFIG 3 /* more boards to configure */
```
## expansion.library
AmigaOS provides `expansion.library` to manage Zorro configuration:
```c
#include <libraries/expansion.h>
#include <clib/expansion_protos.h>
/* Find a configured board by manufacturer/product */
struct ConfigDev *cd = NULL;
while ((cd = FindConfigDev(cd, MANUF_ID, PROD_ID)) != NULL) {
APTR base = cd->cd_BoardAddr;
ULONG size = cd->cd_BoardSize;
/* use board at base */
}
```
**Key structures:**
```c
struct ConfigDev {
struct Node cd_Node;
UBYTE cd_Flags;
UBYTE cd_Pad;
struct ExpansionRom cd_Rom; /* copy of autoconfig ROM area */
APTR cd_BoardAddr; /* configured base address */
ULONG cd_BoardSize;
UWORD cd_SlotAddr;
UWORD cd_SlotSize;
APTR cd_Driver;
struct ConfigDev *cd_NextCD;
ULONG cd_Unused[4];
};
```
## DiagArea — Card ROM
Cards with `ERTB_DIAGVALID` have a small ROM (DiagArea) that the OS calls during boot:
```c
struct DiagArea {
UBYTE da_Config; /* flags */
UBYTE da_Flags;
UWORD da_Size;
UWORD da_DiagPoint; /* offset to diagnostic code */
UWORD da_BootPoint; /* offset to boot code */
UWORD da_Name; /* offset to name string */
UWORD da_Reserved01;
UWORD da_Reserved02;
};
```
The boot vector is called by `ConfigChain()` during the early boot sequence — this is how SCSI controllers install their filesystem handlers.
See [AutoConfig Protocol](autoconfig.md) for the full hardware-level specification — CFGIN/CFGOUT mechanics, nibble-pair ROM format, size codes, shut-up behavior, and FPGA implementation notes. See [expansion.library](../../11_libraries/expansion.md) for the software API (`FindConfigDev`, `ConfigBoard`, `ConfigDev` structure) and manufacturer ID tables.
## Real-World Performance & Bottlenecks