A500

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.

Technical specifications:

• Motorola 68000 (32-bit CISC microprocessor with 16 registers lacking MMU for memory protection and virtual memory)
• 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
• 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)

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