Function:

Bound checks a register against limits and generates exception 5 if the
value falls outside the limit. On NEC CPUs the mnemonic is apparently also
referred to as 'CHKIND'.
Note that the mem component refers to two consecutive memory locations, of
size 'reg' which contain the lower and upper limit for the value in 'reg'
as [low limit][high limit].


    word            dword
    dword           qword

Normally, on Intel 286+ CPUs, the exception saves the CS:IP pointing TO the
BOUND instruction. On the NEC V20, the saved CS:IP point to the instruction
following the BOUND instruction.

According to Intel's documentation the 186 handles this exception the same
way the NEC does. It has been verified on a 486 that the CS:IP of BOUND on
that CPU indeed points TO the instruction itself and not the following one.

Also, contrary to what one might expect, BOUND only allows word or dword
registers to be tested. Byte registers are invalid.

(V20 supplied by Robert Mashlan)
(186 difference & 'CHKIND' supplied by Anthony Naggs)




Breakpoint errors while debugging
──────────────────────────────────────────────────────────────────────────────