Monday, February 13, 2006

A500

A500[EXTRACT]

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For the A-road in England, see A500 road.

The A500, also known as the Amiga 500, was the first "low-end" Commodore Amiga 16-bit multimedia home/personal computer model. It was released in 1987, at the same time as the high-end A2000, and competed directly against the Atari 520ST.

An Amiga 500 computer system, with 1084S RGB monitor and A1010 floppy disk drive.
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An Amiga 500 computer system, with 1084S RGB monitor and A1010 floppy disk drive.

Technical specifications:

  • Motorola 68000 (32-bit CISC microprocessor with 16 registers lacking MMU for memory protection and virtual memory) running at 7.16 MHz (NTSC version), 7.09 MHz (PAL version)
  • Default operating system AmigaOS 1.2 or 1.3 (having 32-bit pre-emptive multitasking microkernel) depending on the revision
  • 512 KB of Chip RAM by default (sound buffers, graphics buffers and software existed in the same memory space)
    • upper limit of 16 MB of memory due to MC68000 limitations (24-bit external address bus)
  • OCS/ECS chipset
  • 50 Hz PAL and 60 Hz NTSC TV output by default versions available; 50/60Hz mode switchable by software in later revisions
  • software-switchable low-pass audio filter (power LED shows filter status, darker when off)
  • IRQ sharing (like the PCI bus)
  • IRQ system had 7 priority levels of interrupts
    • No limit on number of interrupts available
    • Resources handled by Autoconfig, very similar to ACPI, resources were not numbered or labelled, just given as amounts and addresses
  • No specific I/O ports, instead using memory mapped I/O space separately for each hardware device (thanks to Jay Miner)

Amiga 500 was used a lot for gaming, and there were a variety of Atari-style game controllers that could be used. One of the most popular ones was TAC-2, The Totally Accurate Controller mk2 by Suncom.


                List of Commodore microcomputers

MOS Technology 6502-based (8-bit):   MOS/CBM KIM-1 | PET/CBM | CBM-II (aka B/P series) | VIC-20/VC-20 | C64 | SX-64 | C16 & 116 | Plus/4 | C128

M68K-based (16/32-bit):   Amiga 1000 | Amiga 500 | Amiga 2000 | Amiga 500+ | Amiga 2500 | Amiga 3000, UX, T | Amiga 600 | Amiga 1200 | Amiga 4000


The A500 designation was also used on an internal Acorn Archimedes development machine [1].

The A500 often featured the words "The B-52s Rock Lobster" written on the motherboard, in reference to the popular song of that time period.