AN2203 Freescale Semiconductor / Motorola, AN2203 Datasheet - Page 60

• Manufacturer Part Number: AN2203
• Description: MPC7450 RISC Microprocessor Family Software Optimization Guide
• Manufacturer: Freescale Semiconductor / Motorola

MPC7450 Execution Latencies
Appendix A
MPC7450 Execution Latencies
This appendix lists the MPC750, MPC7400, and MPC7450 instruction execution latencies. Instructions are
sorted by mnemonic, primary, extend, form, unit, and cycle.
A high level summary of execution latencies is given in Table A-1. In particular, note that MPC7450 load
latencies are 1–2 cycles longer than MPC750/MPC7400 latencies. The MPC7450 has higher clock
frequencies than the MPC750 and MPC7400. Also, the execution latencies for the FPU and VPU are
significantly longer.
The following tables specify unit assignments, latencies/throughput, and serialization issues for each branch
instruction. Note the following:
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Add, shift, rotate, logical
Multiply (32-bit)
Divide
Load int
Load float
Load vector
Floating-point single (add, mul, madd)
Floating-point single (divide)
Floating-point double (add)
Floating-point double (mul, madd)
Floating-point double (divide)
Vector simple
Vector permute
Vector complex
Vector floating-point
Pipelined load/store and floating-point instructions are shown with cycles of total latency and
throughput cycles separated by a colon (3:2 means 3-cycle latency with throughput of 1 every 2
cycles). Floating-point instructions with a single entry in the cycles column are not pipelined.
Some unit assignments have changed between designs. The reorganization
of the assignments of SRU/IU1/IU2 in the MPC750/MPC7400 to IU1/IU2
in the MPC7450 is a major change. Some MPC7400 vector instructions
executed by the VSIU of the VALU have also moved for the MPC7450: vsl
and vsr are now executed by the VPU, and mfvscr, mtvscr, vcmpbfp,
vcmpeqfp, vcmpgefp, vcmpgtfp, vmaxfp, and vminfp are now executed by
the VFPU. Note that on the MPC7450, the single field form of mtcrf is
executed by the IU1 and is no longer serialized, which should make it
much more useful.
MPC7450 RISC Microprocessor Family Software Optimization Guide
Instruction
Table A-1. Execution Latency in Processor Clock Cycle
Freescale Semiconductor, Inc.
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Go to: www.freescale.com
NOTE
MPC750
19
17
31
—
—
—
—
—
1
6
2
2
3
3
4
MPC7400
19
17
31
1
6
2
2
2
3
3
3
1
1
3
4
MPC7450
23
21
35
1
4
3
4
3
5
5
5
1
2
4
4
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