# Time Model and Cycles

Domain: machine timing and cycles
Function: normative

Didactic companion: [`../learn/mental-model-time-and-cycles.md`](../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:

```text
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

```text
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

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

Frame 18231:
Used: 5,612 cycles

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