Service manual

Glossary-2 Sun Ultra 2 Series Service Manual • July 1996
the number of events, or signal changes, that occur in 1 second. Because one
event can actually encode more than one bit in high-speed digital
communications, baud rate and bits per second are not always synonymous,
and the latter is the more accurate term to apply to modems. For example, a so-
called 9600-baud modem that encodes four bits per event actually operates at
2400 baud but transmits 9600 bits per second (2400 events times 4 bits per
event) and thus should be called a 9600-bps modem.
BMX Buffered memory crossbar. Provides a three-port crossbar connecting a 144-bit
UPA data bus, a 288-bit-wide DRAM memory bus, and a 72-bit UPA data bus.
boot Sometimes referred to as “bootstrap”. To load the system software into
memory and start it running.
boot PROM Contains the PROM monitor program, a command interpreter used for
booting, resetting, low-level configuration, and simple test procedures.
bus (1) A circuit over which data or power is transmitted, one that often acts as a
common connection among a number of locations. (2) A set of parallel
communication lines that connect the major components of a computer system,
including CPU, memory, and device controllers.
CBT Memory data multiplexer and de-multiplexer. A two-port switch electrically
connected between a 576-bit memory bus (DSIMM side) and a 288-bit memory
bus (BMX side).
CD-ROM Compact disc, read-only memory. A form of storage characterized by high
capacity (roughly 600 megabytes) and the use of laser optics rather than
magnetic means for reading data.
chip (1) A small chunk of silicon bearing the equivalent of a large number of
electrical components. (2) An integrated circuit (IC).
CMOS Complementary metal-oxide semiconductor. A semiconductor device that uses
both NMOS (negative polarity) and PMOS (positive polarity) circuits. Since
only one of the circuit types is on at any given time, CMOS chips require less
power than chips using just one type of transistor. This makes them
particularly attractive for use in battery-powered devices, such as portable
computers. Personal computers also contain a small amount of battery-
powered CMOS memory to hold the date, time, and system setup parameters.
codec An encoder-decoder.
console A terminal, or a dedicated window on the screen, where system messages are
displayed.
CRC Cyclic redundancy check. An error check in which the check key is generated
by a cyclic algorithm.(2) A system of error checking performed at both the send
and receiving station after a block-check character (BCC) has been
accumulated.