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   comp.sys.apple2      Discussion about Apple II micros      56,720 messages   

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   Message 55,194 of 56,720   
   Steve Nickolas to qkumba   
   Re: ProDOS boot block?   
   29 Dec 21 13:27:59   
   
   From: usotsuki@buric.co   
      
   On Wed, 29 Dec 2021, qkumba wrote:   
      
   >> 0100- B8 01 02 MOV AX, 0201   
   >> 0103- 41 INC CX   
   >> 0104- 9C PUSHF   
   >> 0105- 06 PUSH ES   
   >> 0106- 53 PUSH BX   
   >> 0107- EA 4C 00 00 00 JMP 0000:004C   
   >>   
   >> 12 bytes, eh? That's far more efficient than I'd come up with. xD   
   >   
   > The instruction at 0107 should read   
   >   
   > 0107- 26 FF 26 4C 00 JMP FAR ES:[004C]   
   >   
   > It has to be indirect to use the vector.   
   > If you're willing to bet that DS is also zero, then you can drop the first   
   26.   
   >   
      
   Didn't know you could use a segment override with JMP. o.o   
      
   The 8086 is a lot more complicated than the 6502.   
      
   (I'm also trying to write a 6502 core in 8086 asm but given that I don't   
   even have a fully working 6502 core in C, it's probably a fool's errand.)   
      
   -uso.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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