MC7457RX1267LC Datasheet, PDF (6/71 Pages) Freescale Semiconductor, Inc – Microprocessor

Features
— Space must be available in the CQ for an instruction to dispatch (this includes instructions that
are assigned a space in the CQ but not in an issue queue)
• Rename buffers
— 16 GPR rename buffers
— 16 FPR rename buffers
— 16 VR rename buffers
• Dispatch unit
— Decode/dispatch stage fully decodes each instruction
• Completion unit
— The completion unit retires an instruction from the 16-entry completion queue (CQ) when all
instructions ahead of it have been completed, the instruction has finished execution, and no
exceptions are pending.
— Guarantees sequential programming model (precise exception model)
— Monitors all dispatched instructions and retires them in order
— Tracks unresolved branches and flushes instructions after a mispredicted branch
— Retires as many as three instructions per clock cycle
• Separate on-chip L1 instruction and data caches (Harvard architecture)
— 32-Kbyte, eight-way set associative instruction and data caches
— Pseudo least recently used (PLRU) replacement algorithm
— 32-byte (eight-word) L1 cache block
— Physically indexed/physical tags
— Cache write-back or write-through operation programmable on a per-page or per-block basis
— Instruction cache can provide four instructions per clock cycle; data cache can provide four
words per clock cycle
— Caches can be disabled in software.
— Caches can be locked in software.
— MESI data cache coherency maintained in hardware
— Separate copy of data cache tags for efficient snooping
— L1 cache supports parity generation and checking
— No snooping of instruction cache except for icbi instruction
— Data cache supports AltiVec LRU and transient instructions
— Critical double- and/or quad-word forwarding is performed as needed. Critical quad-word
forwarding is used for AltiVec loads and instruction fetches. Other accesses use critical
double-word forwarding.
• Level 2 (L2) cache interface
— On-chip, 512-Kbyte, eight-way set associative unified instruction and data cache
— Fully pipelined to provide 32 bytes per clock cycle to the L1 caches
— A total nine-cycle load latency for an L1 data cache miss that hits in L2
MPC7457 RISC Microprocessor Hardware Specifications, Rev. 8
6
Freescale Semiconductor