Instruction Execution Timing
OEP. In many cases, a non-standard instruction requires multiple cycles to execute and the
operation is decomposed into a series of “standard” cycles.
The MC68060 definition of a standard instruction is:
The instruction requires a maximum of one set of extension words.
The instruction makes a maximum of one memory access.
The resources required by the instruction are completely specified by the operation
The standard instruction group is subdivided into two classes:
pOEP | sOEP This class identifies those standard instructions which may be executed
in either the primary or secondary OEP. This group represents all
standard single-cycle instructions.
pOEP-only This class of standard instructions may be executed in the primary OEP
only. This class includes all multi-cycle standard instructions.
The non-standard instruction group is subdivided into three classes:
pOEP-until-last Many of the non-standard instructions represent a combination of
multiple “standard” operations. As an example, consider the
memory-to-memory MOVE instruction. This instruction is decomposed
into two standard operations: first, a standard read cycle followed by a
standard write cycle. This class allows a standard single-cycle
instruction to be dispatched from the sOEP during the last cycle of its
pOEP execution.
pOEP-only This class of non-standard instructions may only be executed in the
primary OEP.
pOEP-but- This class of non-standard instructions requires that the
allows-sOEP operation be performed in the primary OEP, but allows standard
instructions of the pOEP | sOEP class to be dispatched to the
secondary OEP.
Given these instruction classifications, consider Table 10-1 which defines Test 2 of the
superscalar dispatch algorithm of the OEP:
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