Motorola 68000 series

The Motorola 68000 family, m68k and 68k also called 680x0 or, is a series of CISC microprocessors from Motorola.

Were used processors of this family in many home computers such as the Atari ST, Amiga, Apple Macintosh, in servers, for example, of Apollo, Hewlett- Packard and Sun Microsystems, as well as in game consoles such as the Atari Jaguar and Sega Mega Drive. In the field of embedded systems are descendants of this family ( 683xx ) still in use today.

All processors in this series have a simple but powerful instruction set with many addressing modes and operand sizes of 8, 16 and 32-bit. Example, there is the data transfer command "move" that can copy as a true two- address command a date from a memory location to another without having to go through a CPU register. The byte order of the 68k family is big-endian.

Members of this family

  • Motorola 68000
  • Motorola 68008
  • Motorola 68010
  • Motorola 68012
  • Motorola 68020, Motorola 68EC020
  • Motorola 68030, Motorola 68EC030
  • Motorola 68040, Motorola 68EC040, Motorola 68LC040
  • Motorola 68060, Motorola 68EC060
  • Motorola CPU32 (Motorola 68330 )
  • Motorola Coldfire
  • Motorola Dragonball
  • Motorola 68440 - two-channel DMA controller for the 68000/10
  • Motorola 68450 - four-channel DMA controller for the 68000/10
  • Motorola 68451 - external MMU for 68000/10
  • Motorola 68851 - external MMU for 68020
  • Motorola 68881 - External FPU for the 68020 and 68030
  • Motorola 68882 - External FPU for the 68020 and 68030

History

The series begins in 1979 with the Motorola 68000th It has an internal 32 -bit register, a self-addressed with 32- bit linear address space, a 16- bit ALU and a 16- bit data bus. Outwardly he only has 24 address lines, so real are not usable 4 GiB but only 16 MiB memory, which at that time but did not constitute a relevant constraint.

The Motorola 68008 is a version of the 68000 wide with an 8-bit data and a 20 -bit wide address bus. Besides their use as main processor, for example, in the Sinclair QL, this CPU was often used as a controller in the control engineering.

Little success was the Motorola 68010, which fixed some errors of 68000. Especially the handling of memory access errors was improved, which was necessary for the proper support an MMU. In addition, the pipeline received a special mode of short loops of two commands significantly accelerated by these were carried out without repeated reading of the instructions.

The Motorola 68012 was a variant of the 68010, with the additional address lines can address up to 2 GiB memory allowed.

With the Motorola 68020 processor has been completely converted to 32- bit, decreed for the first time about a cache for instructions (size: 256 bytes) and could easily be used with the 68851 FPU 68881 or 68882, or MMU. The affordable 68EC020 had, however, been performed only 24 address lines.

The Motorola 68030 was a programmable integrated MMU, with the help of Virtual memory management was possible, and separate cache for data ( 256 bytes) and instructions ( 256 bytes). The 68EC030 or 68EC040 lacked the internal MMU.

FPU has been integrated with the Motorola 68040 and the on-chip level one cache increased to 4 KiB. Through internal clock doubling brings a 68040 with 25 MHz about the integer processing power of a clocked with 50 MHz 68030th When 68LC040 but lacked the FPU or was shut down due to a defect.

The Motorola 68060 offered a significant performance improvement over the 68040; he allowed clock frequencies up to 75 MHz (available were mostly but clock frequencies of 50 MHz) and was able to perform thanks to " superscalar " up to two integer instructions per clock. But he was mainly used for embedded applications, since the processors from Intel were much cheaper because of the much larger numbers, with servers now found mainly RISC processors use and with the PowerPC already a marketable technical successor in PC and workstation range available stood. Except in some advanced Amiga computers and as an embedded system of the Motorola 68060 was practically no longer apply.

Developments with modified and partially extended command set, represent the Motorola ColdFire and Motorola Dragonball processors, the latter coming in the PDAs from Palm to use.

Typical 68k operating systems are OS-9, AmigaOS, Atari TOS, Mac OS, MiNT, Linux68k, NetBSD and OpenBSD.

Apollo Computer Hewlett-Packard Freescale DragonBall Controller (computing) Floating-point unit Memory Management Unit Palm, Inc. List of microprocessors List of Intel microprocessors Motorola 6809 PowerPC e200 PowerPC e300 PowerPC 7xx PowerPC G4 QorIQ
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