MPC7457(2004) Просмотр технического описания (PDF) - Freescale Semiconductor

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MPC7457
(Rev.:2004)

RISC Microprocessor Hardware Specifications

Freescale Semiconductor 

Features

The memory storage subsystem supports the MPX bus protocol and a subset of the 60x bus protocol to main memory

and other system resources. The L3 interface supports 1, 2, or 4 Mbytes of external SRAM for L3 cache and/or

private memory data. For systems implementing 4 Mbytes of SRAM, a maximum of 2 Mbytes may be used as cache;

the remaining 2 Mbytes must be private memory.

Note that the MPC7457 is a footprint-compatible, drop-in replacement in a MPC7455 application if the core power

supply is 1.3 V.

2 Features

This section summarizes features of the MPC7457 implementation of the PowerPC architecture.

Major features of the MPC7457 are as follows:

• High-performance, superscalar microprocessor

— As many as four instructions can be fetched from the instruction cache at a time.

— As many as three instructions can be dispatched to the issue queues at a time.

— As many as 12 instructions can be in the instruction queue (IQ).

— As many as 16 instructions can be at some stage of execution simultaneously.

— Single-cycle execution for most instructions

— One instruction per clock cycle throughput for most instructions

— Seven-stage pipeline control

• Eleven independent execution units and three register files

— Branch processing unit (BPU) features static and dynamic branch prediction

– 128-entry (32-set, four-way set associative) branch target instruction cache (BTIC), a cache of

branch instructions that have been encountered in branch/loop code sequences. If a target instruction

is in the BTIC, it is fetched into the instruction queue a cycle sooner than it can be made available

from the instruction cache. Typically, a fetch that hits the BTIC provides the first four instructions

in the target stream.

– 2048-entry branch history (BHT) with 2 bits per entry for 4 levels of prediction—not-taken, strongly

not-taken, taken, and strongly taken

– Up to three outstanding speculative branches

– Branch instructions that do not update the count register (CTR) or link register (LR) are often

removed from the instruction stream.

– Eight-entry link register stack to predict the target address of Branch Conditional to Link Register

(bclr) instructions

— Four integer units (IUs) that share 32 GPRs for integer operands

– Three identical IUs (IU1a, IU1b, and IU1c) can execute all integer instructions except multiply,

divide, and move to/from special-purpose register instructions

– IU2 executes miscellaneous instructions including the CR logical operations, integer multiplication

and division instructions, and move to/from special-purpose register instructions

— Five-stage FPU and a 32-entry FPR file

– Fully IEEE 754-1985 compliant FPU for both single- and double-precision operations

– Supports non-IEEE mode for time-critical operations

MPC7457 RISC Microprocessor Hardware Specifications, Rev. 5

Freescale Semiconductor

3

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