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   comp.lang.asm.x86      Ahh, the lost art of x86 assembly      4,675 messages   

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   Message 4,414 of 4,675   
   R.Wieser to All   
   Re: FPU (x87) code debugging.   
   09 Aug 21 18:11:26   
   
   From: address@nospicedham.not.available   
      
   Robert,   
      
   > It is a purer memory test.   
      
   In what way ?     And mind you, I already adressed that.   
      
   > I thought there was question of whether FXSAVE was available   
   > or supported on your CPU.   
      
   As I could not get a working FXSAVE encoding I started to doubt.   
      
   > This checks opcode encoding too.   
      
   No need for that, as those two bytes came from an opcode list.   The only   
   unknown part was the adressing of the target memory.   
      
   > All GP registers should be available at all times.   
      
   Agreed.   But it is an extra factor, and as such interference.   
      
   > Encoding should not be a guessing game.   
      
   What makes you think I was ?      I tried a few different R/M encodings   
   (while providing different registers), and none of them wanted to work.   
   Hence my (above) described doubt to if the command was available on my   
   'puter/processor. (read: I was quite certain I did it "by the book")   
      
   But when you /know/ something ought to work and you cannot make it so than a   
   pragmatic approach will be called for.  Which includes throwing everything   
   and the kitchen sink at it to see if /something/ will work.  And from that   
   try to reason back why it does and where you went wrong with the first   
   attempts.   
      
   > x86 has quirky indirect addressing modes that   
   > are unlikely to yield to trial-and-error.   
      
   True.  But I would not be looking for those.    Just a simple one that   
   /does/ function.  From that foot-in-the-door the rest often follows.   
      
   And that is effectivily what happened when Wolfgang supplied me with a   
   working encoding for FXSAVE [EDI] : while trying to match the 0x07 to the   
   mod,reg,r/m tables I had used I realized I had been using the wrong one.  It   
   was as simple as that.   
      
   Regards,   
   Rudy Wieser   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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