
MOTOROLA
Glossary of Terms and Abbreviations
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Glossary-5
MEI state (E) in which only one caching device contains
data that is also in system memory.
Execution synchronization.
A mechanism by which all instructions in
execution are architecturally complete before beginning execution
(appearing to begin execution) of the next instruction. Similar to
context synchronization but doesn't force the contents of the
instruction buffers to be deleted and refetched.
Exponent.
In the binary representation of a floating-point number, the
exponent is the component that normally signifies the integer power
to which the value two is raised in determining the value of the
represented number. See also
Biased exponent
.
F
Fall-through (branch fall-through).
A not-taken branch. On the G2 core,
fall-through branch instructions are removed from the instruction
stream at dispatch. That is, these instructions are allowed to fall
through the instruction queue through the dispatch mechanism,
without either being passed to an execution unit and or given a
position in the CQ.
Feed-forwarding.
A G2 feature that reduces the number of clock cycles that
an execution unit must wait to use a register. When the source
register of the current instruction is the same as the destination
register of the previous instruction, the result of the previous
instruction is routed to the current instruction at the same time that it
is written to the register file. With feed-forwarding, the destination
bus is gated to the waiting execution unit over the appropriate source
bus, saving the cycles which would be used for the write and read.
Fetch.
Retrieving instructions from either the cache or main memory and
placing them into the instruction queue.
Finish.
Finishing occurs in the last cycle of execution. In this cycle, the CQ
entry is updated to indicate that the instruction has finished
executing.
Floating-point register (FPR).
Any of the 32 registers in the floating-point
register file. These registers provide the source operands and
destination results for floating-point instructions. Load instructions
move data from memory to FPRs and store instructions move data
from FPRs to memory. The FPRs are 64 bits wide and store
floating-point values in double-precision format.
F
Freescale Semiconductor, Inc.
n
.