ASA-EMulatR Reference Guide > Introduction > Architecture Overview > Chapter 21 – Debugging, Tracing, and Determinism > 21.10 Architectural Invariants (Normative)

The following invariants govern the debugging, tracing, and determinism subsystem. Violating any invariant invalidates emulator credibility.

Observational Only: Tracing and logging must never affect architectural behavior. Trace hooks observe committed state, do not inject ordering, do not alter timing, and do not allocate memory in hot paths. Enabling or disabling tracing must not change the sequence of architectural state transitions.

Determinism Enforceability: Given the same initial state, inputs, and configuration (with deterministic scheduling mode enabled), the emulator produces identical architectural outcomes. This includes instruction retirement order, exception delivery order, interrupt timing relative to cycles, and SMP interactions.

Replay Exactness: Deterministic replay produces identical execution — every architectural state transition, fault delivery, and SMP synchronization event is reproduced. Replay depends on deterministic scheduling mode being enabled during recording.

Precise Debug Events: Breakpoints and watchpoints trigger only at architectural boundaries. No debug event fires mid-instruction. When a debug event triggers, architectural state is fully consistent — no partial instruction effects exist.

Interrupt Sampling: Interrupts are sampled at defined run-loop points, not injected. The sampling point is deterministic (instruction boundaries, before fetch). No interrupt may arrive mid-instruction.

SMP Reproducibility: With deterministic scheduling mode enabled, SMP behavior is fully reproducible. Cross-CPU events are correlated via cycle-stamped, CPU-identified trace records.

Host Independence: Host scheduling, host thread timing, and host system load must never influence architectural outcomes. All host-dependent interactions are mediated through emulator-controlled synchronization points.

See Also: Chapter 11 - Architectural Invariants (complete invariant reference).