CEVA-XM4系统组成：
1,VP (vector processor) main DSP core
2,PMSS (program memory subsystem)
3,DMSS (data memory subsystem)
指令集架构：
1，VLIW : very long instruction word 并行
2，SIMD : single instruction multipe data 优化
物理构成：
1，SPU (scalar processing units) X4
2，LSU (load/store units) X2
256 bit/cycle each
3，PCU (program control unit ) X1
4，VPU (vector progress unit) X2
5，PSU (power scaling unit) X1
6，MSS (memory subsystem) X1
register file：
1,general register file(GRF)-->
SPUs, LSUs and PCU use
包含32个32bit registers 每个可以做成这些矢量类型：int、short、char、float
2,vector register file(VRF) 包含40个256bit的vector register
(1) general-purpose registers :V0-V39 (32 个) 每个可表示： vX.f8,vX.i8,vX.s16,vX.c32
(2)accumulators :V24-V39 (16个) 双reg组成512bit accumulator: i16=vW0.i8+vW1.i8, short32=vW0.s16+vW1.s16
V24-V31可复用
3,predicate register file(PRF)
(1)predicate register :scalar operations 15个 prX 大小：1byte
(2)vector predicate registers 7个 vprX 大小：32bit
4,address register file(ARF)
(1) astack pionter
(2) modulo registers
(3) step registers
5,system register file(SRF)
