c9d447f2be
- rtl/w11a - pdp11_sequencer.vhd: tbit logic overhaul 2, now fully 11/70 compatible - tools/tcode - cpu_details.mac: add A4.4 part 0,8,9,10 - cpu_mmu.mac: use m*pd
1.1 KiB
Known differences between SimH, 11/70, and w11a
SimH: trap and interrupt service order has J11 behavior
The 11/70 (and the 11/45) differ from all other PDP-11 models in the order in which interrupts and traps are honored after the successful completion of an instruction. On the 11/70, interrupts have precedence over T-bit trace traps, on all other models interrupts have the lowest priority.
As consequence, RTI can be used on an 11/70 to exit from an interrupt driver,
and exactly one trace trap will happen when an interrupt is honored after
a traced instruction. On all other models, RTT can be used to exit from
an interrupt driver to prevent a double trace trap, one before the interrupt
and one after the hander exit.
SimH uses the J11 service order with interrupts having the lowest priority for all PDP-11 models.
The w11 implements the 11/70 service order. This is verified in a tcode, the test is modified when executed on SimH (see cpu_details.mac test A4.4 part 3).
See also traced WAIT.
Tested with SimH V3.12-3.