From: nowhere@never.at   
      
   On 13.07.2021 05:28, muta...@gmail.com wrote:   
   ...   
   >>> No, I won't use 32-bit instructions.   
      
   >> with the prefix it is still a valid (386) 16 bit instruction!   
      
   > Ok, I'm after instructions that work on both an 80386 in   
   > protected mode (adding a x'66' is fine) and an 8086   
   > (with or without the ignored x'66').   
      
   > Basically the intention is to get the C compiler to generate   
   > 16-bit instructions that work in either environment, adding   
   > an x'66' when it knows it needs to.   
   >   
   > Is there enough instructions that will work this way?   
      
   Not much.   
      
   >>> If I just have bb 44 33, will it work on both the 8086   
   >>> and the 80386?   
      
   >> Yes as long 386 is in RM or PM16,   
      
   > No, I don't want that. I want PM32.   
      
   >> but it become a five byte   
   >> opcode in PM32:   
   >> bb 44 33 22 11 MOV ebx.imm32   
   >> or a four byte:   
   >> 66 bb 44 33 MOV bx.imm16   
      
   > This 4 byte one looks like it will work on both PM32   
   > and RM16.   
   >   
   > That's exactly what I'm after.   
      
   > It will all work, right?   
      
   No, the 66 override reverses the default operand size.   
   so it makes 16 bit within PM32 and 32 bit within PM16/RM.   
   __   
   wolfgang   
      
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