Amiga Boot Sequence
Following the hardware check, the Amiga starts its disk-based boot sequence.
- Checks available boot devices for a valid RDB. This can be the onboard SCSI or IDE controllers, or a peripheral device with its own boot ROM. Some early controllers are not RDB compliant and require a custom preparation of an attached drive. These drives may fail to boot on other controllers.
- Finds the device with the highest boot priority. This is usually the floppy drive DF0:. With no disk in the drive, the system moves on to the device with the next highest priority. If no bootable device is found, the Kickstart screen appears.
- Executes the bootblock of the device. (Some games use a custom bootblock which activates a nonstandard bootup – usually to decrunch compressed game data).
- An AmigaDOS bootblock assigns SYS: to the active device and executes SYS:S/Startup-Sequence, a script.
- The Startup-Sequence prepares the system for use by running SetPatch?, activating assignments for Devs:, Libs, etc. It also runs other small programs to prepare the Workbench.
- A line in the Startup-Sequence causes the User-Startup to be executed. The User-Startup is designed for user-customization of the system. Additional assigns can be made and other programs can be executed here.
- The Workbench is loaded by the LoadWB command.
- The contents of the SYS:WBStartup drawer are run.
- The Shell running the Startup-Sequence is closed.
- The system is ready for use.
Diagnostic menu ran from Kickstart which is activated by holding down both mouse buttons when (re)booting. This is often called the “Early Startup Menu” and contains settings to alter the boot process, degrade for compatibility with old programs and diagnose system faults. Some functions are similar to a PC’s BIOS but, as befits a GUI driven computer, everything is mouse-driven. The following is an ASCII diagram of the menu (for Kickstart 3.x – anyone know if there are any differences for 2.x?)
|-------------------------------------------------------| | Amiga Early Startup Control | (press a key to toggle the display between NTSC and PAL) | | | Boot Options... | | Display Options... | | Expansion Board Diagnostic... | | | | | | | | | |Boot Boot With No Startup-Sequence | |-------------------------------------------------------|
Boot Options
On the left side of the screen is a list of bootable devices, where you can select one to boot from. The list on the right side (“Control Active Devices” displays information about all drives. Clicking on a device’s line will enable/disable it. At the bottom of the screen is a checkbox labeled “Disable CPU Caches. The cache present on the 68020, 68030, 68040 and 68060 can distrupt old programs, so checking this may improve compatibility.
Display Options
Here, you can switch between NTSC and PAL output and select the Custom Chipset to use. AGA users should select “Best Available” to fully exploit their machine, but degrading to ECS (“Enhanced”) or OCS (“Original”) may help with compatibility. Users of ECS will not be able to select AGA, and OCS Amigas have no option here.
Expansion Board Diagnostic
This screen will also automatically display if an expansion board fails. It displays columns for the Board Number (i.e. 1 for the first board, 2 for the second…), Manufacturer (a code identifying the board’s maker), Product (a code identifying the type of board) and whether it’s working or not. Unlike diagnostics programs running under the OS, this does not attempt to name the board, but if your Amiga is malfunctioning this may be the only information you can get.
Boot
This boots the computer, with the options set in the menu.
Boot With No Startup Sequence
This boots the computer with the selected options, but will not run the startup-sequence, leaving you in a basic Shell.