From: nowhere@nevernet.at   
      
   On 10/02/2022 15:47, James Harris wrote:   
   ...   
   > It seems a bit of a conundrum and leads to the obvious question: exactly   
   > what differences are there between instruction decoding in real mode and   
   > in PM16 (the mode immediately after setting CR0 bit 0?   
      
   > As I say, this is all largely academic but if you happen to know the   
   > answer without doing any research do say as the details look interesting.   
      
   1. this EB 00 after write CR0 were never required, at least not by me.   
   2. setting PE does nothing on its own, the CPU remain in real mode until   
       the far jump which changes interpretation from segment to descriptor.   
       and its a 16:16 code without prefix   
      
   my RM->PM switches look like:   
     MOV eax,CR0   
     OR eax,1   
     MOV CR0,eax   
     push 0x20        ;prepared selectors   
     pop ds   
     push 0x20        ;20=flat data   
     pop es   
     push 0x10        ;10=restricted stack   
     pop ss   
     mov esp.0000xxxx   
     jmp 0018:PM16   or  jmp 66 0028:PM32 or even jmp 66 0038:LM64   
      
   PMl6:   
   ...   
   PM32:   
   ...   
   __   
   wolfgang   
      
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