# Decision 0002: BIOS Policy

Status: `Locked`

## Context

The project needed a firmware strategy that balanced authenticity with
bring-up practicality.

Main approaches considered:

- real BIOS only,
- HLE-only BIOS behavior,
- real BIOS with narrowly-scoped debug stubs.

## Options considered

1. Real BIOS only.
2. HLE-only BIOS strategy.
3. Real BIOS plus narrow debug stubs.

## Decision

Adopt `real BIOS plus narrow debug stubs`.

Policy details:

- Real user-supplied BIOS images remain the primary firmware path.
- Debug stubs are allowed only where they materially shorten early bring-up.
- Stubs must be narrow, explicit, and temporary.

Every stub must be tracked in a decision record or equivalent design note with:

- owner,
- purpose,
- scope boundary,
- removal condition.

## Consequences

- The project stays anchored to real PS2 boot behavior.
- Early bring-up may proceed without waiting for every subsystem to be complete.
- There is a maintenance cost: stub behavior must not silently become the
  architecture.
- The repository must never include Sony BIOS images.
- The stub-module plan must call out which stubs are in play for each phase.
