The Timing and Buffer Ledger

Ada audits the timing and buffer ledger — clock drift, sample offset, buffer fill, and outage backlog

ADA · CALCULATION AUDIT

Foundations · optional mathematics and physics

The Timing and Buffer Ledger

The chapter treats timing and buffering as a conservation check: a 50 ppm oscillator drifts about 180 ms in an hour, which is 18 samples of error on a 100 Hz stream, and a 64 KB buffer holds only about 13 seconds of a 4.8 KB/s stream. Every rate must convert to seconds, samples, or bytes before the contract is trusted. This audit works the timing and buffer ledger line by line.

Companion to the chapter Acquisition Timing and Buffer Contracts — every number here comes from that chapter.

Clock drift, sample offset, buffer fill, and outage backlog, ~4 minutes

Ada: Treat timing and buffering as a conservation check. Convert every rate into seconds, samples, bytes, or records before trusting the acquisition contract.

The ledger

Clock drift = 3600 s x 50 / 1,000,000 = 0.18 s = 180 ms in one hour

100 Hz sampling period = 1 / 100 s = 0.01 s = 10 ms

Sample offset = 180 ms / 10 ms = 18 samples, so the vibration streams no longer align

Data rate = 100 records/s x 48 bytes/record = 4800 bytes/s = 4.8 KB/s

64 KB buffer time = 64,000 bytes / 4800 bytes/s = 13.333 s, which supports the chapter's about 13 seconds claim

Two-minute outage backlog = 120 s x 4800 bytes/s = 576,000 bytes = 576 KB

1,000-record ring buffer at 100 records/s holds 1,000 / 100 = 10 s of raw records; keeping the newest 1 s reserves 100 raw records and forces an explicit policy for older evidence

Every number above is taken from the chapter's own timing and buffer example and re-derived step by step.