14 Facts About Motorola 68000


In 1982, the Motorola 68000 received a minor update to its instruction set architecture to support virtual memory and to conform to the Popek and Goldberg virtualization requirements.

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Encrypted variants of the Motorola 68000, being the Hitachi FD1089 and FD1094, store decryption keys for opcodes and opcode data in battery-backed memory and were used in certain Sega arcade systems including System 16 to prevent piracy and illegal bootleg games.

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Motorola 68000's version is called the MC68HC000, while Hitachi's is the HD68HC000.

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Later evolution of the Motorola 68000 focused on more modern embedded control applications and on-chip peripherals.

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The Motorola 68000 continued to be widely used in printers throughout the rest of the 1980s, persisting well into the 1990s in low-end printers.

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Motorola 68000 was successful in the field of industrial control systems.

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Users of such systems do not accept product obsolescence at the same rate as domestic users, and it is entirely likely that despite having been installed over 20 years ago, many Motorola 68000-based controllers will continue in reliable service well into the 21st century.

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In October 1995, the Motorola 68000 made it into a handheld game console, Sega's Genesis Nomad, as its CPU.

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Motorola 68000 has a 24-bit external address bus and two byte-select signals "replaced" A0.

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However, the dual stack pointer design of the Motorola 68000 makes this normally unnecessary, except when a task switch is performed in a multitasking system.

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The 68EC000 and 68SEC000, which are later derivatives of the Motorola 68000, do meet the requirements as the "MOVE from SR" instruction is privileged.

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Motorola 68000 is unable to easily support virtual memory, which requires the ability to trap and recover from a failed memory access.

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The Motorola 68000 does provide a bus error exception which can be used to trap, but it does not save enough processor state to resume the faulted instruction once the operating system has handled the exception.

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Several companies did succeed in making Motorola 68000-based Unix workstations with virtual memory that worked by using two Motorola 68000 chips running in parallel on different phased clocks.

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