The ceiling on integration, as simulated seconds per second of wall clock.
Not the ceiling on time warp: a tick every entity coasts through is propagated from an epoch and jumped rather than stepped (ADR-0025), and there is no rate at which that can be too fast. What this bounds is the ticks a frame runs one at a time — a thrusting ship, a descent through air.
A fixed budget of 8 ticks per frame is the right guard against a stalled
frame and the wrong one for a deliberate one, and for a long time this class
could not tell the difference. The measurement: at 60 fps a budget of 8
delivers 480 ticks per second, which is 7.5× real time — so of the seven
detents the dev dock offers, from 1× to 100,000×, everything past 5× was
identical and every tick above it went straight into droppedTicks. Silently:
the clock was scrupulous about reporting the drops and nothing displayed them
next to the number they contradicted.
1,920× is 2048 ticks in a 60 Hz frame, which is ~1.6 ms at the ~1.25M ticks/s measured in-browser for one entity — inside a 16.6 ms frame with room for a machine several times slower. It is a measured number and not a principled one; when the benchmark harness can say what a tick costs here, this should be derived from a share of the frame rather than pinned.
A rate, and not a count per frame, and that is load-bearing. The budget used to be a flat 2048 ticks per frame, which meant that once warp saturated it — anything past ~1,920×, so both of the top two detents, always — the clock delivered a constant 32 simulated seconds every frame however long the frame took. Simulated time then advanced per frame instead of per second, so its rate was modulated by frame-time noise: ±2 ms of jitter at 60 fps is ±12% of the sim rate, every frame. Everything in the scene inherits that, but what makes it visible is a body's speed measured in its own radii, and Phobos and Deimos cover 0.19 and 0.22 of their own radius per second against 0.072 for the next worst (Mimas) and 0.0006 for Luna. They vibrated by a full body width at 10,000× while every other moon in the Solar System held still.
simulation/src/clock.ts:73