From: mutazilah@nospicedham.gmail.com   
      
   On Saturday, November 19, 2022 at 11:37:49 PM UTC+8, Terje Mathisen wrote:   
      
   > > if @DataSize   
   > > else   
   > >   
   > > mov bx,ss   
   > > mov ax,ds   
   > > sub bx,ax   
   > > mov cl,4   
   > > shl bx,cl   
   > >   
   > > mov bp, sp   
   > > sub bp, bx   
      
   This should have been an add, not a subtract. :-)   
      
   > > mov ss, dx   
   > > mov sp, bp   
   > > ; And that null PSP thing needs to be redone   
   > > mov ax, 0   
   > > push ax   
   > >   
   > > endif   
   > >   
   > >   
   > > My testing suggests that there is a problem with tiny memory   
   > > model, but the other memory models seem to work.   
      
   > Tiny is the one used by all .COM files, in those the binary has no   
   > relocation info, it is just block copied into a newly allocated 64KB   
   > block of memory, at offset 100h, and with those first 256 bytes (the   
   > PSP) initialized by the OS.   
   >   
   > In this model all segment registers are the same, i.e. CS=DS=ES=SS   
   > because the OS and CPU are pretending to be a Z80 with no support for   
   > extended/segmented memory addressing.   
      
   That's only if you deliberately choose to produce a COM file,   
   and also you need an org 100h in the startup code.   
      
   Otherwise, tiny memory model produces a perfectly fine   
   normal MSDOS executable, and the entry point can be   
   anywhere.   
      
   My hello world program, linking in the whole C library   
   in tiny memory model is this size:   
      
   Memory size:  e110 (57616.)   
      
   _TEXT                  CODE           DGROUP         0000:0000       000053c6   
   CONST                  DATA           DGROUP         053c:0006       000002be   
   CONST2                 DATA           DGROUP         0568:0004       00000000   
   _DATA                  DATA           DGROUP         0569:0000       00000668   
   _BSS                   BSS            DGROUP         05cf:0008       00006412   
   STACK                  STACK          DGROUP         0c11:0000       00002000   
      
   Entry point address: 0000:02fa   
      
   Which is cool.   
      
   I have a lot of BSS because of 6144-byte buffers for files which   
   gave a great speedup on a real XT in the 1990s.   
      
   My tiny mode doesn't support malloc though, so you can't   
   do much. Doesn't support parameters either. :-) Large is   
   fine though. It was interesting to see.   
      
   PDOS/86 now has INT 3 and INT 1 support as a result of   
   debugging that.   
      
   BFN. Paul.   
      
   --- SoupGate-Win32 v1.05   
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