::To: All  From: Tom Torfs  Subj: XT compatability  ::
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 TT> * Original message posted in: 80xxx.
 TT> * Crossposted in: comp.lang.asm.x86.
 TT> Hello All!
 TT> I'm having a problem here with a program that works fine on 286 and
 TT> above, but  never fails to crash on an XT with a 8088 CPU (it seems to
 TT> get in some sort of  infinite loop, and if I try to press ctrl-alt-del
 TT> it hangs completely).
 TT> Now I'm sure my program doesn't use any 186+ instructions, so that's
 TT> not the  problem. There is also the fact that 8088 divide by zero
 TT> handler return address  points at the next instruction instead of the
 TT> divide instruction, but I take  that into account also.
 TT> Do any of you have some suggestions as to what the cause of this 
 TT> incompatability may be ? Most likely it's got something to do with how
 TT> the CPU  handles certain instructions and traps, such as int 1 etc.
Ok...there's a number of things that can cause problems.
Some versions of the 8088 chip have a bug in the way the stack is managed...
If you modify the stack registers (SS or SP), first clear the interrupt
flag...as sometimes a hardware interrupt will get generated.
Avoid use of the string instructions
(err...STOSB/STOSW/CMPSB/CMPSW/LODSB/LODSW/etc), as in many cases they
weren't accepted on some systems (My old TEC (Toshiba) had that problem...
they would work, but the next instruction would be corrupted).
Are you playing with the interrupt vector table, out of curiosity?
Well..hope this helps, but I would really like more information (or source).
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