wfjm.w11/doc/simh_diff_div_after_v1.md

Known differences between SimH, 11/70, and w11a

SimH: State of N and Z and registers after a DIV abort with V=1

The state of the N and Z condition codes is specified as unspecified for the DIV instruction when V=1 is set after a zero divide or an overflow condition. See 1979 processor handbook on page 75.

The 11/70 leaves the N and Z condition codes and the result registers in a state depending on the abort point in the microcode state flow. That results in sometimes surprising settings.

SimH returns Z=0 and N based on the sign of the full 32-bit result, as can be easily determined by xor'ing of the sign bits of dividend and divisor.

xxdp ekbbf0 test 15 tests the exact 11/70 behavior to verify the divide logic and is skipped.

w11 also returns Z=0 and N based on the sign of the full 32-bit result, this is documented as w11 known difference.