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PowerPC Architecture Compliance
7-2
MPC801 USER’S MANUAL
MOTOROLA
7
7.1.4 Exceptions
Invocation of the system software for any exception caused by an exception in the core is
precise, regardless of the type and setting.
7.1.5 The Branch Processor
7.1.6 Fetching Instructions
The core fetches many instructions into its internal buffer (the instruction prefetch queue)
prior to execution. If a program modifies the instructions it intends to execute, it should call
a system library program to ensure that the modifications are visible to the instruction
fetching mechanism prior to executing the modified instructions.
7.1.7 Branch Instructions
The core implements all the instructions for the branch processor according to the
User Instruction Set Architecture Book I
. For details about the performance of various
instructions, see Table 8-1 of this manual.
PowerPC
7.1.7.1 INVALID BRANCH INSTRUCTION FORMS
Bits marked with
z
in the BO encoding definition are discarded by the core decoding. Thus,
these types of invalid form instructions yield results of the defined instructions with the
zero. If the decrement and test CTR option is specified for the
the target address of the branch is the new value of the CTR. Condition is evaluated
correctly, including the value of the counter after decrement.
z
bit
bcctr
or
bcctrl
instructions,
7.1.7.2 BRANCH PREDICTION
The core uses the
branch conditions. No prediction is done for branches to the link or count register if the target
address is not ready. See Table 6-1 for more details.
y
bit to predict path for prefetch. Prediction is only done for not-ready
7.1.8 The Fixed-Point Processor
The core implements the following fixed-point instructions:
Arithmetic instructions
Compare instructions
Trap instructions
Logical instructions
Rotate and shift instructions
Move to/from system register instructions
All hardware instructions for the fixed-point processor are defined in the
Instruction Set Architecture Book I
. For details about the performance of various
instructions, see Table 8-1 of this manual.
PowerPC
User