prometeu-runtime/docs/runtime/specs/01-time-model-and-cycles.md

Time Model and Cycles

Domain: machine timing and cycles Function: normative

Didactic companion: ../learn/mental-model-time-and-cycles.md

1 Scope

This chapter defines the temporal contract of the PROMETEU machine.

It covers:

• machine base clock;
• logical frame structure;
• cycle accounting;
• per-frame budget;
• CAP interaction with time measurement.

2 System Base Clock

PROMETEU operates with a fixed 60 Hz logical clock.

This means:

• 60 iterations of the machine loop per second;
• each iteration corresponds to one logical frame;
• the logical clock is stable regardless of host platform.

3 Logical Frame

A PROMETEU frame represents a complete unit of machine execution.

Conceptual stage order:

FRAME N
INPUT
UPDATE
DRAW
AUDIO
SYNC

The machine guarantees:

• fixed stage order;
• deterministic repetition;
• no implicit extra frames between logical frame boundaries.

4 PROMETEU Cycles

4.1 Definition

A PROMETEU cycle is the abstract unit used to measure execution cost inside the machine.

• VM instructions consume documented cycle cost;
• peripheral operations also consume cycle cost;
• cycle cost is independent of host wall-clock timing.

4.2 Properties

Cycles are:

• countable;
• comparable;
• stable across supported hosts;
• suitable for certification and profiling.

5 Per-Frame Budget

Each frame has a maximum cycle budget.

This budget:

• is reset every frame;
• does not accumulate unused cycles;
• represents the capacity of the virtual execution envelope for that frame.

5.1 Conceptual Example

Frame Budget: 10,000 cycles

Used:
- Update logic: 4,200
- Draw calls: 3,100
- Audio: 900

Remaining:
1,800 cycles

6 Work Distribution Over Time

PROMETEU does not require all logic to run every frame.

Machine-visible work may be distributed over time, for example:

• enemy logic every 2 frames;
• pathfinding every 4 frames;
• timers based on frame count;
• subsystem-specific update cadence.

Such distribution changes cycle pressure and is part of the observable execution model.

7 CAP Interaction

The CAP defines contextual technical limits such as:

• maximum cycle budget per frame;
• memory limits;
• peripheral call limits.

7.1 CAP Does Not Block Execution

Fundamental rules:

• the game always runs;
• the game can always be packaged;
• the game can always be played.

CAP does not prevent execution.

7.2 CAP Generates Evidence

When CAP is active, PROMETEU measures and records:

• average cycle usage per frame;
• cycle peaks;
• problematic frames;
• cost distribution.

These data feed certification artifacts without changing cartridge semantics.

8 Time-Based Certification

PROMETEU certification may analyze:

• average cycle usage per frame;
• maximum peaks;
• problematic frames;
• dominant cost sources.

8.1 Conceptual Example

Target CAP: PROMETEU-LITE
Frame Budget: 5,000 cycles

Frame 18231:
Used: 5,612 cycles

Primary cause:
enemy.updateAI(): 1,012 cycles