Motorola 68020
processor
A microprocessor from Motorola. It was the successor to the Motorola 68010 and was followed by the Motorola 68030. The 68020 has 32-bit internal and external data and address buses and a 256-byte instruction buffer, arranged as 64 direct-mapped 4-byte entries[?].
The 68020 added many improvements to the 68010 including a 32-bit ALU and external data bus and address bus, and new instrucitons and addressing modes. The 68020 (and 68030) had a proper three-stage pipeline.
The new instructions included some minor improvements and extensions to the supervisor state, some support for high-level languages which didn’t get used much (and was removed from future 680×0 processors[?]), bigger (32 x 32-bit) multiply and divide instructions, and bit field manipulations.
The new adderessing modes added another level of indirection to many of the pre-existing modes, and added quite a bit of flexibility to various indexing modes and operations.
The instruction buffer (an instruction cache) was 256 bytes, arranged as 64 direct-mapped 4-byte entries. Although small, it made a significant difference in the performance of many applications.
The 68881 and the faster 68882 FPU chips could be used with the 68020.
The 68020 was used in many models of the Apple Macintosh II series of personal computers and Sun 3 workstations.
(2001-03-07)
Read Also:
- Motorola 68030
processor A 32-bit microprocessor in Motorola’s Motorola 68000 family, with on-chip split instruction and data cache of 256 bytes each. The 68030 has an on-chip MMU (except in the 680EC30 version). The 68881 and the faster 68882 FPU chips could be used with the 68030. The 68030 was the successor to the Motorola 68020, and […]
- Motorola 68040
processor (MC68040) A microprocessor from Motorola. It was the successor to the Motorola 68030 and was followed by the Motorola 68060. The 68040 was the first 680×0 family member with an on-chip FPU. It also had split instruction and data caches of 4 kilobytes(?) each. It was fully pipelined, with six stages. The 68040 was […]
- Motorola 68050
There was no 68050. The successor to the Motorola 68040 was the Motorola 68060. The even numbers (68000, 68020, 68060) were reserved for major revisions to the 680×0 core. The odd numbers (68010, 68030, 68050) were minor upgrades from the previous chip. For example, the Motorola 68010 was a Motorola 68000 with some minor enhancements […]
- Motorola 68060
processor A 32-bit microprocessor from Motorola, the successor to the Motorola 68040. The 68060 is the highest performance 680×0 family processor currently (April 1995) available. It has 2 to 3 times the performance of the 68040. The 68060 is probably the last development from Motorola in the high performacnce 680×0 series. They don’t want to […]
- Motorola 6809
(MC6809) An eight-bit microprocessor from Motorola, Inc. The 6809 was a major advance over both its predecessor, the Motorola 6800 and also over the 6502. The 6809 had two 8-bit accumulators, rather than one in the 6502, and could combine them into a single 16-bit register. It also featured two index registers and two stack […]