Editing Autoconfig

{{short description|Amiga system for automatically setting up hardware peripherals}}
{{distinguish|GNU Autoconf}}
{{more footnotes|date=August 2008}}
'''Autoconfig''' is an [[auto-configuration]] protocol of [[Amiga]] computers which is intended to automatically assign resources to expansion devices without the need for [[jumper (computing)|jumper]] settings.<ref name="amiga_hardware_ref">{{cite book | last=Miner | first=Jay | authorlink=Jay Miner | title=Amiga Hardware Reference Manual | edition=Third | series=Amiga Technical Reference Series | year=1991 | publisher=Addison-Wesley | isbn=0-201-56776-8 | url=https://archive.org/details/amiga-hardware-reference-manual-3rd-edition}}</ref>  It is analogous to [[PCI Configuration Space|PCI configuration]] through [[Advanced Configuration and Power Interface|ACPI]].<ref>{{cite web |url=https://www.minitool.com/lib/acpi.html |title=What Is ACPI (Advanced Configuration and Power Interface)? |last=To |first=Acpi |date=3 July 2020 |orig-date=April 29, 2021 |access-date=2021-04-29 }}</ref><ref>{{cite web |url=http://theamigamuseum.com/amiga-kickstart-workbench-os/kickstart/kickstart-1-2/ |title=The Amiga Museum » Kickstart 1.2 |last=Received |first=Intuition |orig-date=April 29, 2021 |access-date=2021-04-29 }}</ref>

Autoconfig is integrated within the Amiga's [[Kickstart (Amiga)|Kickstart]] firmware, usually stored in [[read-only memory|ROM]].
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.

== Protocol ==
Expansion devices respond to certain fixed memory addresses starting at  hexadecimal {{nowrap|0xE8 0000}} (or {{nowrap|0xFF00 0000 }} for [[Zorro III]]) if the /CFGIN signal is asserted and the device is not already configured. The [[Central processing unit|CPU]] reads [[nibble]]s of configuration information (usually supplied by a [[Programmable array logic|PAL]]) 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 a [[backplane]] design such as the [[Amiga 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 backplane [[Logical disjunction|OR]]s 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 one [[7400 series|74LS32]] (quad OR gate) on the Amiga 2000, which is the only [[motherboard]] hardware required by Autoconfig.<ref>{{cite web |url=http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node02C7.html |title=K / AUTOCONFIG(TM) / The Autoconfig Mechanism |last=Pic |first=The |orig-date=April 29, 2021 |access-date=2021-04-29 }}</ref>

== Hardware specifications and bus connections ==
Autoconfig is part of the [[Zorro II]] and [[Zorro 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 the [[Amiga 1000]]. Zorro II is a relatively straightforward extension of the [[68000]] bus.<ref name="a500-2000_tech">{{citation | url=http://www.bombjack.org/commodore/amiga/amiga-commodore/Amiga_A500_A2000_Technical_Reference_Manual_1987.pdf | last=Finkel | first=Steve | title=Commodore Amiga A500/A2000 Technical Reference Manual | publisher=Commodore-Amiga, Inc. | year=1987 | access-date=2011-09-03 | archive-url=https://web.archive.org/web/20120613032004/http://www.bombjack.org/commodore/amiga/amiga-commodore/Amiga_A500_A2000_Technical_Reference_Manual_1987.pdf | archive-date=2012-06-13 | url-status=dead }}</ref> 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 in [[PCI Local Bus|PCI]], 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 with [[Industry Standard Architecture|ISA]] slots. The Zorro bus and ISA bus can be connected by means of a "bridgeboard", such as, the Janus Hardware Emulator, which allows emulation of [[Intel]] [[80286]] or [[80386]] systems.<ref name="a500-2000_tech"/>

Zorro III is the 32 bit auto-configuring expansion bus of [[Amiga 3000]] and [[Amiga 4000]] systems.<ref name="zorro3">{{cite web | title=The Zorro III Bus Specification | url=http://www.thule.no/haynie/zorroiii/docs/zorro3.pdf | first=Dave | last=Haynie | date=20 March 1991 | publisher=Commodore-Amiga, Inc. | access-date=31 January 2010 | archive-url=https://web.archive.org/web/20120716212151/http://www.thule.no/haynie/zorroiii/docs/zorro3.pdf | archive-date=16 July 2012 | url-status=dead }}</ref> 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.

==Notation==
In early Commodore documents it was styled ''Auto Configuration'',<ref name="a500-2000_tech"/> ''auto-config''<ref name="a500-2000_tech"/> or ''AutoConfig'',<ref name="a2000_intro">{{citation | url=http://www.bombjack.org/commodore/amiga/amiga-commodore/Amiga_2000_Introduction.pdf | title=Introduction to the Commodore Amiga 2000 | year=1987 | publisher=Commodore-Amiga, Inc. | access-date=2011-09-03 | archive-url=https://web.archive.org/web/20120613032141/http://www.bombjack.org/commodore/amiga/amiga-commodore/Amiga_2000_Introduction.pdf | archive-date=2012-06-13 | url-status=dead }}</ref> whereas in later documents it was styled ''AUTOCONFIG''.<ref name="zorro3"/>

==References==
{{Portal|Amiga}}
{{reflist}}

==External links==
* [http://wiki.amigaos.net/wiki/Amiga_Hardware_Manufacturer_ID_Registry Amiga Hardware Manufacturer ID Registry]

{{Amiga hardware}}

[[Category:Amiga]]
[[Category:AmigaOS]]
[[Category:Computer buses]]
[[Category:Computer configuration]]