Fragment 38 of 72 · drawer 04
Track, sector, and waiting arc
A non-scale diagram of two mechanical searches required before a logical address can become readable data.
- Accession
- MW-F-038
- Representative period
- Interpretive mechanism plate
- Drawer
- Diagrams & specimens
- Certainty
- high
Track, sector, and waiting arc
Interpretive mechanism plate
Observed surface
CONCENTRIC TRACK: where the head must first be positioned.
SECTOR ARC: the requested region may still be rotating away from the head.
WAITING ARC: distance travelled by the disk after seek ends and before reading can begin.
Implied procedure
A head move and a disk revolution are independent motions whose delays add.
At 300 revolutions per minute, one full turn occupies 200 milliseconds; position decides how much of it is paid.
Interpretive residue
The plate treats latency as geometry.
Even when the head has reached the right circle, the desired data may be physically elsewhere in time.
Accountability record
Evidence beneath the reconstruction.
These institutional sources support the mechanism or historical practice interpreted above. They do not contain this reconstructed record, its wording, or its invented values.
- IBM History · 2021 The floppy disk IBM's history of flexible-disk development, including the original 8-inch medium, its operational purpose and the format's later mass adoption. Open institutional record ↗
- IBM Support · technical reference 1.44 MB 3.5-inch SlimLine diskette drive specifications A vendor specification used for the representative 300 rpm mechanism; one revolution takes 200 ms, making half a revolution 100 ms. Open institutional record ↗