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122 lines
2.8 KiB
Markdown
122 lines
2.8 KiB
Markdown
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[← Home](../README.md) · [Boot Sequence](README.md)
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# DOS Boot — Bootstrap, Mount List, Startup-Sequence
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## Overview
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After the Kickstart ROM initialises the kernel and resident modules, `dos.library` takes over to mount filesystems and run the user's startup scripts.
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---
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## Boot Sequence Flow
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```
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Kickstart ROM init complete
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↓
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dos.library creates initial CLI process
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↓
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BootStrap module (strap) reads boot block from boot device
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↓
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Boot block executed (OFS/FFS bootblock code)
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↓
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Mount configured devices from MountList (DEVS:DOSDrivers/)
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↓
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Execute S:Startup-Sequence
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↓
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Execute S:User-Startup
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↓
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LoadWB (start Workbench)
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```
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---
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## Boot Block Format
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The first 2 sectors (1024 bytes) of a bootable disk:
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```
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Offset Size Description
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$000 4 Boot block ID: "DOS\0" (OFS), "DOS\1" (FFS), etc.
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$004 4 Checksum (complement to zero)
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$008 4 Root block pointer (usually 880)
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$00C ... Boot code (up to 1012 bytes of 68000 code)
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```
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### Boot Block Types
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| ID | Hex | Type |
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|---|---|---|
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| `DOS\0` | `444F5300` | OFS (Old File System) |
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| `DOS\1` | `444F5301` | FFS (Fast File System) |
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| `DOS\2` | `444F5302` | OFS + International |
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| `DOS\3` | `444F5303` | FFS + International |
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| `DOS\4` | `444F5304` | OFS + Dir Cache |
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| `DOS\5` | `444F5305` | FFS + Dir Cache |
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| `DOS\6` | `444F5306` | OFS + Long Filenames (OS 3.2) |
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| `DOS\7` | `444F5307` | FFS + Long Filenames (OS 3.2) |
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---
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## Boot Priority
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Devices are booted in priority order. Highest priority device boots first:
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| Device | Default Priority | Description |
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|---|---|---|
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| DF0: | 5 | First floppy drive |
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| DH0: | 0 | First hard disk partition |
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| DH1: | −5 | Second partition |
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| DF1: | −10 | Second floppy |
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Set in mountlist: `BootPri = 0` or via HDToolBox.
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---
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## Startup-Sequence
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Standard `S:Startup-Sequence` for OS 3.1:
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```
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C:SetPatch QUIET ; apply ROM patches
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C:AddBuffers DH0: 50 ; filesystem buffers
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C:Version >NIL:
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FailAt 21
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MakeDir RAM:T RAM:Clipboards RAM:ENV RAM:ENV/Sys
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Copy >NIL: ENVARC: RAM:ENV ALL NOREQ
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Assign >NIL: T: RAM:T
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Assign >NIL: CLIPS: RAM:Clipboards
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Assign >NIL: REXX: S:
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Assign >NIL: PRINTERS: DEVS:Printers
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Assign >NIL: KEYMAPS: DEVS:Keymaps
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Assign >NIL: LOCALE: SYS:Locale
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Assign >NIL: LIBS: SYS:Classes ADD
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Assign >NIL: HELP: LOCALE:Help DEFER
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C:IPrefs
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ConClip >NIL:
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; Launch Workbench:
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LoadWB
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EndCLI >NIL:
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```
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---
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## Early Startup Control (Boot Menu)
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Hold **both mouse buttons** during boot to access the Early Startup Control menu:
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| Option | Description |
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|---|---|
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| Boot With No Startup-Sequence | Skip S:Startup-Sequence |
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| Boot Standard | Normal boot |
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| Boot With: [device list] | Select boot device |
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| Display Mode: [NTSC/PAL] | Override display standard |
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---
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## References
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- RKRM: Boot chapter
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- NDK39: `dos/dosextens.h` — BootStrap
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