MPC7457 datasheet(4/68 Pages) FREESCALE

4 / 68 page

MPC7457 RISC Microprocessor Hardware Specifications, Rev. 5

Freescale Semiconductor

Features

– Hardware support for denormalized numbers

– Thirty-two 64-bit FPRs for single- or double-precision operands

— Four vector units and 32-entry vector register file (VRs)

– Vector permute unit (VPU)

– Vector integer unit 1 (VIU1) handles short-latency AltiVec™ integer instructions, such as vector add

instructions (for example, vaddsbs, vaddshs, and vaddsws)

– Vector integer unit 2 (VIU2) handles longer-latency AltiVec integer instructions, such as vector

multiply add instructions (for example, vmhaddshs, vmhraddshs, and vmladduhm)

– Vector floating-point unit (VFPU)

— Three-stage load/store unit (LSU)

– Supports integer, floating-point, and vector instruction load/store traffic

– Four-entry vector touch queue (VTQ) supports all four architected AltiVec data stream operations

– Three-cycle GPR and AltiVec load latency (byte, half-word, word, vector) with one-cycle

throughput

– Four-cycle FPR load latency (single, double) with one-cycle throughput

– No additional delay for misaligned access within double-word boundary

– Dedicated adder calculates effective addresses (EAs)

– Supports store gathering

– Performs alignment, normalization, and precision conversion for floating-point data

– Executes cache control and TLB instructions

– Performs alignment, zero padding, and sign extension for integer data

– Supports hits under misses (multiple outstanding misses)

– Supports both big- and little-endian modes, including misaligned little-endian accesses

•

Three issue queues FIQ, VIQ, and GIQ can accept as many as one, two, and three instructions, respectively,

in a cycle. Instruction dispatch requires the following:

— Instructions can be dispatched only from the three lowest IQ entries—IQ0, IQ1, and IQ2

— A maximum of three instructions can be dispatched to the issue queues per clock cycle

— 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

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