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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
27 lines
1.2 KiB
Markdown
27 lines
1.2 KiB
Markdown
## Known differences between SimH, 11/70, and w11a
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### SimH: traced `WAIT` has J11 behavior
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On an 11/70 (and an 11/45), a traced `WAIT` will wait until an interrupt happens
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and finish without raising a trace trap because the interrupt has higher
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service precedence. The trace trap related to the `WAIT` will happen when the
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interrupt driver exits with an `RTI`.
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See also [trap and interrupt service order](simh_diff_service-order.md).
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On a J11 and other PDP-11 models, a traced `WAIT` falls through and raises a
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trace trap immediately. This is consistent with trace traps having higher
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precedence in those models.
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SimH uses the J11 service order with interrupts having the lowest priority for
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all PDP-11 models, and consequently, a traced `WAIT` falls through and raises
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a trace trap immediately.
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xxdp program `ekbbf0` test 063 verifies the 11/70 behavior and is skipped
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(see [patch](../tools/xxdp/ekbbf0_patch_1170.scmd)).
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The w11 implements the 11/70 service order and `WAIT` behavior.
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This is verified in a [tcode](../tools/tcode/README.md), the `WAIT` test is
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skipped when executed on SimH
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(see [cpu_details.mac](../tools/tcode/cpu_details.mac) test A4.4 part 4).
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Tested with SimH V3.12-3.
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