Dell PowerEdge 6400 - Manual (Page 24)

Arranged in rows and columns, a pixel is a single point on a video display. Video resolution —640 x 480, for example—is expressed as the
number of pixels across by the number of pixels up and down.
POST
Power-on self-test. Before the operating system loads when you turn on your computer, the POST tests various system components such as RAM,
the disk drives, and the keyboard.
ppm
pages per minute
PQFP
Plastic quad flat pack, a type of microprocessor socket in which the microprocessor chip is permanently mounted.
PRN
A synonym for the MS-DOS device name LPT1.
program diskette set
The set of diskettes from which you can perform a complete installation of an application program. When you reconfigure a program, you often
need its program diskette set.
protected mode
An operating mode supported by 80286 or higher microprocessors, protected mode allows operating systems to implement:
l A memory address space of 16 MB (80286 microprocessor) to 4 GB (Intel386 or higher microprocessor)
l Multitasking
l Virtual memory, a method for increasing addressable memory by using the hard-disk drive
The Windows NT 32-bit operating system runs in protected mode. MS-DOS cannot run in protected mode; however, some programs that you can
start from MS-DOS
—such as Windows—are able to put the computer into protected mode.
PS/2
Personal System/2
PSPB
power-supply paralleling board
PVC
polyvinyl chloride
Q
QIC
quarter-inch cartridge
R
RAM
Random-access memory. The computer's primary temporary storage area for program instructions and data. Each location in RAM is identified by
a number called a memory address. Any information stored in RAM is lost when you turn off your computer.
RAID
Redundant arrays of independent disks. This phrase was introduced by David Patterson, Garth Gibson, and Randy Katz at the University of
California at Berkeley in 1987. The goal of RAID is to use multiple small, inexpensive disk drives to provide high storage capacity and
performance while maintaining or improving the reliability of the disk subsystem.
Patterson, Gibson, and Katz described five different methods, which are known as RAID levels 1 through 5. Each level uses one or more extra
drives to provide a means of recovering data lost when a disk fails, so that the effective failure rate of the whole disk subsystem becomes very low.
Recently, Katz has defined a sixth method, RAID 6, which improves reliability even further, and a configuration that provides no data recovery has
popularly become known as RAID 0.