mc68020

Motorola 68020
68020
MC68020

   <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}.

   (2001-03-07)