Partition
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.
PC
Personal computer.
Personal Storage Division
The Western Digital organization responsible for design, production and sale of hard drives for personal computers.
Platform
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.
Platter
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.
Port
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.
Pre-fetch
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.
Protocol
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.