938 B
Known differences between SimH, 11/70, and w11a
SimH: traced WAIT has J11 behavior
On an 11/70 (and an 11/45) a traced WAIT will wait until an interrupt happens
and finish without raising a trace trap because the interrupt has higher
service precedence. The trace trap related to the WAIT will happen when the
interrupt driver exits with an RTI.
See also trap and interrupt service order.
On a J11 and other PDP-11 models, a traced WAIT falls through and raises a
trace trap immediately. This is consistent with trace traps having higher
precedence in those models.
SimH uses the J11 service order with interrupts having the lowest priority for
all PDP-11 models, and consequently, a traced WAIT falls through and raises
a trace trap immediately.
xxdp ekbbf0 test 63 verifies the 11/70 behavior and is skipped.
The w11 implements the proper 11/70 service order and WAIT behavior.