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Autoconfig is anauto-configuration protocol ofAmiga computers which is intended to automatically assign resources to expansion devices without the need forjumper settings.[1] It is analogous toPCI configuration throughACPI.[2][3]
Autoconfig is integrated within the Amiga'sKickstart firmware, usually stored inROM.When the system is switched on,AmigaOS interrogates each expansion device in turn and assigns address space or resources as needed. For example, in the case of a memory card, the OS can dynamically add the memory to the system. Through Autoconfig the OS can access firmware on expansion devices, for example, to boot from a disk connected to a hard disk controller.
Expansion devices respond to certain fixed memory addresses starting at hexadecimal0xE8 0000 (or0xFF00 0000 forZorro III) if the /CFGIN signal is asserted and the device is not already configured. TheCPU readsnibbles of configuration information (usually supplied by aPAL) such as manufacturer ID, product ID, and the amount of address space the device requires. The CPU then writes a base memory address to the device (or tells it to "shut up" if for some reason it can't be configured), and the device asserts /CFGOUT.
The /CFGIN of the first device is tied to ground. The second device's /CFGIN is controlled by the first device's /CFGOUT, and so on.
In abackplane design such as theAmiga 2000, connecting the /CFGOUT of one slot directly to the /CFGIN of the next would create the problem that an unoccupied slot would break the configuration chain. To solve this, the backplaneORs the /CFGIN and /CFGOUT signals to form the /CFGIN for the next slot (/CFGOUT is pulled low if undriven), which allows empty slots to be bypassed. This requires one74LS32 (quad OR gate) on the Amiga 2000, which is the onlymotherboard hardware required by Autoconfig.[4]
Autoconfig is part of theZorro II andZorro III expansion bus specification for configuring expansion devices in Amiga systems.Zorro II was first used in the Amiga 2000, though a similar expansion bus is present on theAmiga 1000. Zorro II is a relatively straightforward extension of the68000 bus.[5] Autoconfig requires the 68000 data and address bus to be available to all devices on the bus. In theory, a virtual address system, as used inPCI, would require a minor revision to Autoconfig.
The Amiga 2000 can accommodate five Zorro expansion cards, such as, RAM expansions, SCSI controllers and graphic cards. However the standard does not put a limit on the number of devices. In the A2000, two Zorro II slots are aligned withISA slots. The Zorro bus and ISA bus can be connected by means of a "bridgeboard", such as, the Janus Hardware Emulator, which allows emulation ofIntel80286 or80386 systems.[5]
Zorro III is the 32 bit auto-configuring expansion bus ofAmiga 3000 andAmiga 4000 systems.[6] From the A3000 design onwards, it was deemed desirable for all enumerable hardware expansions to use Autoconfig. It is OS-legal for non-Autoconfig hardware to be completely ignored and the standard was adopted in AmigaOS 3.1.
In early Commodore documents it was styledAuto Configuration,[5]auto-config[5] orAutoConfig,[7] whereas in later documents it was styledAUTOCONFIG.[6]
