Compatible Systems RISC 2800i Uživatelský manuál stáhnout pdf (Strana 5)

MPC7448 RISC Microprocessor Hardware Specifications, Rev. 4

Freescale Semiconductor 5

Features

— 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

— Parity support on cache

— 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, 1-Mbyte, eight-way set-associative unified instruction and data cache

— Cache write-back or write-through operation programmable on a per-page or per-block basis

— Parity support on cache tags

— ECC or parity support on data

— Error injection allows testing of error recovery software

• Separate memory management units (MMUs) for instructions and data

— 52-bit virtual address, 32- or 36-bit physical address

— Address translation for 4-Kbyte pages, variable-sized blocks, and 256-Mbyte segments

— Memory programmable as write-back/write-through, caching-inhibited/caching-allowed, and

memory coherency enforced/memory coherency not enforced on a page or block basis

— Separate IBATs and DBATs (eight each) also defined as SPRs

— Separate instruction and data translation lookaside buffers (TLBs)

– Both TLBs are 128-entry, two-way set-associative and use an LRU replacement algorithm.

– TLBs are hardware- or software-reloadable (that is, a page table search is performed in

hardware or by system software on a TLB miss).

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Compatible Systems RISC 2800i Uživatelský manuál Strana 5