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[back to SCSI Terminology index page]
P____________________________
P6
See Pentium Pro.
P7
The code name for a forthcoming CPU chip from Intel.
Packet Writing
A method of writing data on a CD in small increments, as opposed to writing large blocks of information as required by the Track-at-Once and Disc-at-Once methods. Packet writing (also "packet resourcing") allows small packets or pieces of data to be written one packet at a time, lessening the chance of buffer underrun. Packet writing is good only for data tracks.
Parallel
Sending bits in groups ( by 8 or 16 bits).
Parallel Interface
An interface between a computer and a printer in which the computer sends multiple bits of information to the printer simultaneously. Centronics interface is another name for parallel (which is different from Centronics SCSI, however).
Parallel Port
A connection on an IBM PC or compatible computers, usually named LPT1, where you plug in a cable for a parallel printer. Some computers have more than one parallel port and are labeled LPT2, LPT3, etc.
Parallel Printer
A printer with a parallel interface, which you connect to a parallel port.
Parity
An error-checking procedure in which the number of 1s must always be the same- either even or odd- for each group of bits transmitted without error. The parity setting is often important in communications. If you are having difficulty with a modem, check the parity; it can be odd, even, or none.
Parity Checking
A way to verify the accuracy of data transmitted over the SCSI bus. One bit in the transfer is used to make the sum of all the 1 bits either odd or even (for odd or even parity). If the sum is not correct, an error message appears.
Partition
A logical portion of space on a hard disk designated by a drive letter.
Passive Matrix Display
A type of LCD screen used on portable computers in which parallel wires are run both horizontally and vertically in front and behind the display. Pixels are turned on when both the horizontal and vertical wires which intersect the pixel are energized. Residual current in the wires can partially activate other pixels, and reduce contrast in the display. For this reason, the passive matrix display is considered inferior to the active matrix LCD. See also Dual-Scan Display.
Passive Termination
The electrical connection required at each end of the SCSI bus, composed of a set of resistors. It improves the integrity of bus signals.
Passive terminator
The electrical connection required at each end of the SCSI bus, composed of a set of resistors that provides a fixed-value impedance match between the end of the SCSI bus and the cable. It improves the integrity of bus signals. Passive terminators are comprised only of resistors and are susceptible to variations in the power supplied by the host adapter.
See also active terminator; forced-perfect terminator.
Path Table
The Path Table contains the addressed for the Directory Files so that they can be used to directly access the data files.
PC
Personal Computer. Strictly speaking, this refers to the IBM PC, which is any IBM-manufactured personal computer made prior to the PS/2 Series. Usually PC refers to any personal computer compatible with IBMs. It is also used to refer to any personal computer.
PC100 SDRAM
Intel is working with memory vendors to keep up with the performance of faster processors and bus architectures. Intel's goal is to ensure that memory subsystems continue to support evolving platform requirements and to assure that memory does not become a bottleneck to system performance. It is especially important to ensure that the PC memory roadmap evolves together with the performance roadmaps for the processors, I/O and graphics. To meet this goal, Intel has worked with leading DRAM vendors to develop the PC100 SDRAM Component and DIMM specifications. The SDRAM module follow such specifications to production, we called "PC100 SDRAM". You can see PC100 memory module on market in Q2, 1998.
Intel has delivered the PC SDRAM Component Specification, as well as the Serial Presence Detect and 100-MHz DIMM specifications to major vendors and OEMs.
PCA
(Power Calibration Area). A space reserved at the beginning of the disc for calibrating the laser power needed to record to that disc.
P-cable
A 68-wire cable used for 16-bit SCSI-3 buses. P-cables can be used with Q-cables for 32-bit SCSI-buses.
PC Card
See PCMCIA.
PC-DOS
Personal Computer Disk Operating System. A version of MS-DOS licensed by IBM for use on its personal computers.
PCI
Peripheral Component Interconnect. A new standard computer bus, common to newer Macintosh and Pentium machines. This bus features faster bus throughput, as well as hardware compatibility across computer platforms, so a card could be used on both a PCI Mac and a PCI pentium machine, though different software drivers would be needed..
Peripheral Component Interconnect. A local bus specification that allows connection of peripherals directly to computer memory. It bypasses the slower ISA and EISA buses.
PCMCIA
A standard for hardware expansion, mainly for notebook computers. PCMCIA is supported by Macintosh and IBM compatible notebooks, and features ease of use. Often simply called a PC Card.
Pentium
A CPU chip produced by Intel, used in IBM compatible machines. The Pentium is the equivalent of the 586 (of the 80x86 chip family).
Pentium Pro
A CPU chip produced by Intel, which has some substantial architectural changes from the Pentium, including a built in L2 cache. The Pentium Pro was called P6 during development.
Peripheral
A hardware item that can be attached to a computer to increase its functionality, such as a printer or monitor.
Peripheral Devices
A piece of hardware (such as a video monitor, disk drive, printer, or CD-ROM) used with a computer and under the computers control. SCSI peripherals are controlled through a SCSI host adapter.
Phase-Change Technology
Phase-change technology uses only optics to read, write, and erase information. Lasers change the material on the disk between crystalline and amorphous states. Material on the disk heated by a low-power laser becomes crystalline; material heated by a high-power laser becomes amorphous. Data is written to and erased from the disk using lasers to change the state of the material on the disk.
To read data, a laser and lens detect, measure, and translate into data the light that's reflected back from the surface of the disk. Light that strikes an amorphous area is scattered, and very little returns to the lens. Light that strikes a crystalline area is reflected straight into the lens.
Photo CD
A compact disc format based on the CD-ROM XA and Orange Book Hybrid Disc specifications, used to store photographic images for display and printing.
Pin-1 Orientation
The alignment of pin-1 on a SCSI cable connector and the pin-1 position on the SCSI connector into which it is inserted. External SCSI cables are always keyed to insure proper alignment, but internal SCSI ribbon cables are sometimes not.
PIO
Programmed Input/Output. A way the CPU can transfer data to and from memory via the computers I/O ports. PIO is usually faster than DMA, but requires CPU time.
Pipeline
A channel used to transfer commands, data, or signals.
Plug and Play (PnP)
A hardware standard for auto configuration, which requires operating system support. Currently, Windows 95 supports Plug and Play. Also slang for autoconfig.
Plug-in Card
See add-on.
PMA
(Program Memory Area) On a recordable disc, an area which "temporarily" contains the information about the recordings on tdhe disc -- track numbers and their starting and stopping points when tracks are written in a session which is not yet closed. When you do not close the current session, to keep track of all data recorded, a kind of pre-TOC is written to the disc in an area that is only accessible by the CD recorder. When the session is closed, this same TOC information is written in the session lead-in.
PnP
See Plug and Play.
Port
A plug and its associated circuitry in a computer's hardware, used for sending data from computer to its peripherals or to other computers. Serial, parallel, and SCSI ports are commonly used ports.
Port Address
Also Port Number. The Address through which commands are sent to a host adapter board. This Address is assigned by the PCI bus.
Port Number
See Port Address.
POST
Power On Self Test. A set of routines stored in ROM that provides diagnostic tests for various system components before booting can proceed.
Post-Gap
A space dividing tracks, recorded within the track data area at its end. The post-gap is 150 sectors (2 seconds) long and is required only where successive tracks are of different types. However, because many disc replicators expect a post-gap at the end of every track and may erroneously strip out data sectors if they do not find one, Easy-CD Pro Software records a post-gap after every track. See also "About Gaps Between Tracks".
PostScript
A printer language used to describe the text and graphics to be printed.
PowerPC
A new family of CPU chips, produced by an industry group including Motorola, IBM, and Apple. Used in Macintosh and other computers.
PowerPC Platform (PPCP)
A standard hardware architecture developed by a consortium including Apple, IBM, and several other companies. PPCP machines use the PowerPC CPU and a PCI bus. A number of operating systems, including
Copland, AIX, Windows NT, etc. should be able to run on PPCP machines. Also called the Common Hardware Reference Platform (CHRP).
PPCP
See PowerPC Platform.
P-Q Editing
Subchannels that can be manipulated, when recording in disc-at-once mode, which give the user control over the P through Q subchannels for optimal glass mastering.
Processor
A computer hardware component that performs computations directed by software commands.
Protocol
Rules for communicating, particularly for the format and transmission of data.
P-to-A Transition Cable
An adapter used to connect 8-bit SCSI-1 devices using A-cables to a 16- or 32-bit SCSI-3 device using P-cables.
[back to SCSI Terminology index page]
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