优势：前期大步长让元素快速移动到大致位置，后期小步长精细调整
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，这一点在safew官方版本下载中也有详细论述
5C9 SLCTR DESSDT 4 IN=+ ; delay slot 1: compute descriptor address
Besides the Test PLA, the 386 has another PLA called the Entry PLA that maps opcodes to microcode entry points. One of its input bits is a "protected mode" flag. Many instructions have both a real-mode and a protected-mode entry point -- for instance, MOV ES, reg maps to address 009 (a single microcode line) in real mode, but to 580 (which initiates a full descriptor load with protection tests) in protected mode. The trick that makes V86 work is to define this flag as: