Amiga Zorro III

Released as the expansion bus of the Commodore Amiga 3000 in 1990, the Zorro III computer bus was used to attach peripheral devices to an Amiga motherboard. Designed by Commodore International lead engineer Dave Haynie, the 32-bit Zorro III replaced the 16-bit Zorro II bus used in the Amiga 2000. As with the Zorro II bus, Zorro III allowed for true Plug and Play autodetection (similar to the PC's PCI bus) wherein devices were dynamically allocated the resources they needed on boot.

Zorro III continued Zorro II's direct-address design. The CPU could directly address any Zorro III device as memory, so Zorro memory expansions could be made (and were made) as well as it being possible to use video memory on a video card to be as system RAM. Despite being a 32-bit bus, Zorro III used the same 100 way slot and edge connector as Zorro II. The extra address and data lines were provided by multiplexing some of the existing connections with the nature of the lines changing at different stages of the bus access cycle (e.g. address becoming data). This allowed the use of Zorro II expansion cards on the newer bus, coexisting with Zorro III cards. Certain Zorro III cards would also function when connected to the older Zorro II bus, though at Zorro II's reduced data rates.

Links

* [http://www.thule.no/haynie/zorroiii/docs/zorro3.pdf The Zorro III Bus Specification (PDF)]
*List_of_device_bandwidths#_note-4 Notes on Zorro III performance
* [http://amiga.resource.cx/exp/search.pl?intf=z3 Amiga Hardware Database] - Descriptions and photos of Zorro III cards.
* [http://amigahardware.mariomisic.de/index_e.html The Big Book of Amiga Hardware]