Zoned bit recording (ZBR)
Outer tracks are longer, so they get to hold more sectors — otherwise half the platter is wasted.
A track at the outer edge of a platter is physically much longer than one near the hub, yet older disks wrote the same number of sectors on every track and left the rim half empty. Zoned bit recording divides the platter into zones, each getting its own — higher — sector count the further out it sits. The result was tens of percent more capacity on the same surface.
The price is that the true geometry can no longer be expressed as simple cylinder/head/sector numbers — the drive's electronics lie about CHS and quietly translate to LBA.