From: king621@nospicedham.comcast.net   
      
   On 07/18/2018 05:53 AM, R.Wieser wrote:   
   > Bill,   
   >   
   >>    cmd_findfl db 'findfl',0   
   >>   
   >> is commented out the problem goes away.   
   >   
   > Have you already tried what happens when you just comment *that* line out   
   > (and leave the ones following it enabled) ?    My guess is that the   
   > same/similar problem will occur   
      
   Yes, you are right.  I tried that and the same problem occurs.   
      
   >   
   > js2nd dw 0x9e0 ;segment at end of jsec2   
   > ...   
   > mov word[si+6],js2nd  ;segment - where to load sectors   
   >   
   > My assembler complains about that: you cannot do a direct memory-to-memory   
   > copy that way (needs to go thru a register).   Your assembler might be using   
   > the address of js2nd (and not its contents), which would mean that you are   
   > loading a sector over all the variables that follow (including the drive   
   > letter).   
      
   In the actual (greater) program (not posted) it does work fine the first   
   time - the directory listing of the root directory is printed   
   successfully.  If I then change the current drive and do it again it   
   prints the root directory of the previous drive.  It all works fine   
   except the second time the int13/ah=42 fails. Since it works the first   
   time there must be some other problem.   
      
   >   
   > Did you maybe intended to use "equ" (or something like it) there (like   
   > "js2nd equ 0x9e0" or "js2nd = 0x9e0") ?   
   >   
   > Another possibility is that you are somehow trashing the stack.   
   > Could your stackpointer be pointing into the same area where you are loading   
   > your sector ?   
      
   In my 'boot sector' I have the following   
      
   mov	ax,	0   
   mov	ss,	ax   
   mov	sp,	0x600   
   mov	ds,	ax   
      
   mov si, 0		;location of this info packet in data seg.   
   mov word[si],16		;packet size   
   mov word[si+2],16	;# of sectors to xfer   
   mov word[si+4],0x0000	;offset where to load sectors   
   mov word[si+6],0x07e0	;segment where to load sectors   
   mov word[si+8],546	;starting absolute sector# in a quadword   
   mov word[si+10],0	;   
   mov word[si+12],0   
   mov word[si+14],0   
     partition has 1(bs)+512(2FATs)+32(root dir.)+13(text)+3(data)   
     = 545 + 16   
      
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