Glossary of Hard Disk Drive Terminology (Letter P)

A way to logically divide a hard drive so that an operating system treats each partition as a separate hard drive. Each partition has a unique drive letter.

Passive Termination
A termination architecture that is used to match the impedance at the end of the SCSI bus by using a voltage divider network of passive resistors.

Personal computer.

Personal Storage Division
The Western Digital organization responsible for design, production and sale of hard drives for personal computers.

A basic design from which a series of products is engineered and produced. Western Digital’s new, 4.3 GB-per-platter platform, for example, is the basis for five products ranging in capacity from 4.3 to 13.0 gigabytes.

An actual metal (or other rigid material) disk that is mounted inside a fixed-disk drive. Many drives consist of multiple platters mounted on the spindle to provide more data storage surfaces. Each platter may use one or both surfaces to store data.

A connection or socket on the motherboard or controller card. A motherboard may have one or two ports (primary and secondary). If your motherboard has only one port, you may need to add a controller card to create a secondary port.

Instructions that are loaded into a queue when the processor’s external bus is otherwise idle.

Primary Partition
The partition where the operating system files are stored. To start your operating system from a hard disk, it must have a primary partition. You must also make the primary partition active.

Product Road Map
A company’s plan for the introduction of new products.

A convention of data transmission that defines timing, control format, and data representation.

PRML (Partial Response Maximum Likelihood)
A read channel using sampled data, active equalization and Veterbi detection to accurately retrieve the user data off the disk.

Programmed I/O
In a disk drive with an AT interface, data transfers between the drive and host using programmed I/O (PIO). The host uses PIO to write to the Command Block Registers (CBRs) when transmitting control information, such as the location of a read command.

Proximity Recording
A recording technology that increases recording density by allowing the read/write head to come in close proximity to the disk surface.