Page 402 - A Practical Guide from Design Planning to Manufacturing

372 Glossary

NMOS N-type metal oxide semiconductor field-effect transistor.
NOR A logic function that is false if any of its inputs are true.
Northbridge The chipset component responsible for communicating with the
processor and the highest bandwidth components, typically main memory and
the graphics adapter. Also called the memory controller hub (MCH) or graphics
memory controller hub (GMCH).
NOT A logic function that is true if its input is false.
nm Nanometer.
N-type metal oxide semiconductor (NMOS) A MOSFET with N-type source
and drain terminals in a P-well. An NMOS transistor will conduct when the gate
voltage is high.
N-type semiconductor Semiconductor with donor dopants added to create
negative free charge carriers.
OPC Optical proximity correction.
Opcode The bits of an encoded machine language instruction determining the
operation to be performed.

Operating system (OS) The program responsible for loading and running
other programs.
Optical proximity correction (OPC) Changes made to a photolithography
mask to compensate for the wave nature of light.

OR A logic function that is true if any of its inputs is true.
OS Operating system.
Out-of-order execution Executing instructions in a different order than spec-
ified by the software in order to improve performance. The processor must make
sure that the program results are unchanged by this reordering.
PA-RISC Precision architecture reduced instruction set computing. A RISC
computer architecture created by Hewlett Packard.
Parity bits Redundant bits added to memory stores to allow misread bytes to
be detected.
PCA Printed circuit assembly.
PCB Printed circuit board.
PCI Peripheral component interconnect.

PDIP Plastic dual in-line package.
PECVD Plasma-enhanced chemical vapor deposition.
Performance bug A design flaw that causes an integrated circuit to spend more
cycles than intended executing a program but still produce the logically correct
result.