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MPC7448 RISC Microprocessor Hardware Specifications, Rev. 4

4 Freescale Semiconductor

Features

— 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

– A 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 only be dispatched 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

— Retires an instruction from the 16-entry completion queue (CQ) when all instructions ahead of

it have been completed, the instruction has finished executing, and no exceptions are pending

— Guarantees sequential programming model (precise exception model)

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