Margaret Hamilton AGC Priority Executive Simulator

DSKY Primary Display P64 APPROACH

UPLINK ACTY

TEMP

PRIO DISP

RESTART

PROG ALARM

OPR ERR

VERB

NOUN

PROG

R1 (ALT FT): +03240

R2 (V/FPS): -00042

R3 (ALARM): NONE

Scheduler Architecture HAMILTON ASYNC

Hamilton Priority Exec: Preemptive core sets drop low-priority telemetry/radar traps during CPU overload (>100%), keeping DAP thrusters & guidance alive.

Mission Scenarios

Lunar Module Descent Trajectory GUIDANCE LOCKED

AGC 8-Slot Core Set Memory (Vac Area / Job Table) 7/8 SLOTS

SLOT	JOB NAME	PRIO	RATE	CYCLES	STATE

CPU Load & Cycle Stealing Real-Time Telemetry

Workload Injector

Rendezvous Radar Overload

Historical 15% bit-stealing counter trap (12.8 kHz phase lock sync bug).

Landing Radar Interrupt:

DAP Thruster Control:

DSKY Display Refresh:

Telemetry Downlink:

Mission Flight Telemetry

CPU UTILIZATION

114.2%

CORE SATURATION

7 / 8

DROPPED JOBS (SHED)

RESTARTS (1202)

DAP THRUS. LATENCY

19.8 ms

PROPELLANT LEFT

4.8%

Data Export & Logs

Margaret Hamilton AGC Priority Executive Simulator

Read the explanation

During the Apollo 11 lunar descent, a misaligned rendezvous radar flooded the 43.4 kilohertz Apollo Guidance Computer with unexpected cycle-stealing interrupts, pushing CPU demand past 100 percent. Rather than crashing from queue starvation, Margaret Hamilton designed an asynchronous priority executive. The scheduler dynamically ranks jobs, guaranteeing execution slots for critical attitude control and descent servicer routines. When the eight-slot core set table fills, low-priority jobs like display polling and telemetry downlinks are shed. The computer recovers state in milliseconds, triggering alarm 1202 while safely touching down on the lunar surface.