Parallelism

1. The condition of two planes or lines being parallel. Important in disk drives because a lack of it in mechanical assemblies can result in positioning inaccuracy. More precisely: planes-coplanar; lines-colinear.
2. Is the local variation in disk thickness measured independently of thickness itself.
3. The ability of a multiprocessor computer to allocate more than one processor (CPU) to a computing problem, where each CPU works on a separate problem or separate segment of that problem. Also referred to as parallel processing.

 

Parity

A simple method of data error detections that always makes numbers either odd or even, using an extra bit in which the total number of binary 1s (or 0s) in a byte is always odd or always even; thus, in an odd parity scheme, every byte has eight bits of data and one parity bit. If using odd parity and the number of 1 bits comprising the byte of data is not odd, the ninth or parity bit is set to 1 to create the odd parity. In this way, a byte of data can be checked for accurate transmission by simply counting the bits for an odd parity indication. If the count is ever even, an error is indicated.

 

Partition

A logical section of a disk drive, each of which becomes a logical device with a drive letter.

 

PC-Card (PCC)

Also known as PCMCIA

 

PCMCIA

Personal Computer Memory Card International Association.

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Peak Shift

The shifting in time of the zero-slope portion of a readback voltage from the values contained in the write current waveform. Sometimes incorrectly used to describe bit jitter.

 

Peripheral Equipment

Auxiliary memory, displays, printers, and other equipment usually attached to a computer system s CPU by controllers and cables (They are often packaged together in a desktop computer).

 

Phase Locked Loop (PLL)

A circuit whose output locks onto and tracks the frequency of an input signal. Sometimes incorrectly called a data separator.

 

Phase Margin

Measure in degrees of the amount of difference between excursions from the window center where flux reversals can occur and the edge of the data window. Similar to window margin.

 

Physical Sector

The smallest grouping of data on the hard disk; always 512 bytes.

 

PIO

Programmable Input Output. A means of accessing device registers. Also describes one form of data transfers. PIO data transfers are performed by the host processor using PIO register accesses to the data register.

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Plated Thin Film Media

Magnetic disk memory media having its surface plated with a thin coating of a metallic alloy instead of being coated with oxide.

 

Platter

Magnetic disk memory media. Each platter (disk) has two surfaces, the top and bottom surface. Each surface has it's own R/W Head for reading, writing & erasing data.

 

Plug and Play (PnP)

The Plug and Play specification was developed by Microsoft with cooperation from Intel and many other hardware manufacturers. The goal of Plug and Play is to create a computer whose hardware and software work together to automatically configure devices and assign resources. This allows hardware changes and additions without the need for large-scale resource assignment tweaking. As the name suggests, the goal is to be able to just plug in a new device and immediately be able to use it, without complicated setup procedures. PnP for PCs became a reality with the release of Windows 95 and PC hardware designed to work with it.

 

POST (Power On Self-Test)

In a computer system based on one of Intel's x86 processors or compatibles, program execution start at memory location F000:FFF0h. This address is part of ROM BIOS and contains a jump command to a series of BIOS routines that test and initialize the hardware components: the Power-On-Self-Test or POST.

POST consists of various test- and initializationroutines for the on-board hardware and expansion cards such as the video adapter. If a failure is detected this can be made known by:

• one or more audible beeps, the socalled beep codes;
• an error message presented on screen;
• a checkpoint code, sent to one of the system's output ports.

When all tests have been performed and components have been initialized, control is transferred to the Int 19h Bootstrap Loader, to load the available operating system on disk.

 

Prefix

A number and/or letter at the beginning of the model number of Maxtor hard disk drives. This usually denotes the drive family.

 

Processing

The process of the computer handling, manipulating and modifying data such as arithmetic calculation, file lookup and updating, and word pressing.

 

Pulse Crowding

Modification of playback amplitude due to super-positioning of adjacent flux reversal fields being sensed by the read/write gap.

 

Pulse Detect

A digital pulse train in which each leading edge or each edge corresponds to a magnetic transition read from the disk. If transition qualification circuitry exists in the drive, this signal is the output of same. Also known as transition detect.