The '''68020''' is a [[microprocessor]] from [[Motorola]]. It is the successor to the [[Motorola 68010]] and is succeeded by the [[Motorola 68030]].
The 68020 had [[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 [[Arithmetic and Logic Unit]] (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 680x0 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]] (floating point unit) chips could be used with the 68020.
The 68020 was used in many models of the [[Amiga]] and [[Apple Macintosh II]] series of [[personal computer|personal computers]] and [[Sun 3 workstation|Sun 3 workstations]].
For more information on the instructions and architecture see [[Motorola 68000]].
''This article (or an earlier version of it) contains material from [[FOLDOC]], used with [[Public Domain Resources/Foldoc license|permission]].''