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1.1 KiB
1.1 KiB
Known differences between w11a and KB11-C (11/70)
Instruction fetch after SPL
The SPL instruction in the 11/70 always fetched the next instruction
regardless of current mode, pending device, or even console interrupts.
This is known as the infamous SPL bug, see
- https://minnie.tuhs.org/pipermail/tuhs/2006-September/002692.html
- https://minnie.tuhs.org/pipermail/tuhs/2006-October/002693.html
- https://minnie.tuhs.org/pipermail/tuhs/2006-October/002694.html
- https://minnie.tuhs.org/pipermail/tuhs/2006-October/002695.html
- https://minnie.tuhs.org/pipermail/tuhs/2006-October/002701.html
- https://minnie.tuhs.org/pipermail/tuhs/2006-October/002695.html
- https://minnie.tuhs.org/pipermail/tuhs/2006-October/002702.html
In the w11a, the SPL has 11/70 semantics in kernel mode, thus no
traps or interrupts, the instruction after the SPL is unconditionally
executed.
But in supervisor and user mode SPL really acts as NOOP, so traps and
interrupts are taken as for all other instructions.
--> The w11a isn't bug compatible with the 11/70.