<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 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 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.
Motorola 68000 « Motorola 6801 « Motorola 68010 «
Motorola 68020 » Motorola 68030 » Motorola 68040
» Motorola 68050