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17 lines
704 B
Markdown
17 lines
704 B
Markdown
## Known differences between SimH, 11/70, and w11a
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### SimH: Red stack zone `PSW` protection
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The 11/70 includes location 177776 in the red stack zone. This is not
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documented in the Processor Handbooks, only mentioned in the Technical
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Manual. It was added to protect the `PSW` in case a further stack push
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is done after an emergency stack was set up, the vector flow of a fatal
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stack errors had concluded, and the handler does a stack push when `SP`
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is still 0.
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SimH doesn't support this behavior.
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w11 implements the `PSW` protection. This is verified in a
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[tcode](../tools/tcode/README.md), the test is skipped when executed on SimH
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(see [cpu_details.mac](../tools/tcode/cpu_details.mac) test A3.2).
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