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- Multistation Access Unit. The hub of the
Token Ring network architecture and can connect
as many as eight nodes. Often referred to by the
IBM specification of 8228.
MBR - Master Boot Record. A record created
during the boot process after the first harddisk
is identified by the ROM initialization code.
The first 446 bytes of this record are a program
that is to be executed. The rest of the record
is a two byte header and four 16 byte table entries
to define up to four partitions. These can be
four Primary partitions or three Primary Partitions
and one extended partition contain Logical Volumes.
The MBR program reads the first 512 byte sector
from the Primary Partition into storage. It then
jumps to the program in that sector.
The Master Boot Record, also known as the a partition
table, is the sector located at cylinder 0, head
0, sector 1, or LBA 0. This sector is created
by an FDISK utility program. The MBR may be the
only partition table sector, or the MBR may be
the first of multiple partition table sectors
that form a linked list. A partition table entry
can describe the starting and ending sector addresses
of a partition (also known as a logical volume
or a logical drive) in both L-CHS and LBA form.
Partition table entries use the L-CHS returned
by INT 13H AH=08H. Older FDISK programs may not
compute valid LBA values.
MCA - Micro Channel Architecture. A type
of computer bus design or architecture introduced
by IBM in 1987. Largely obsolete today, the MCA
bus ran at 10 MHz. A proprietary standard established
by IBM to take over from ISA, and therefore incompatible
with anything else. It comes in two versions,
16- and 32-bit and, in practical terms, is capable
of transferring around 20 Mbps. Developed by IBM
for the PS/2 line of computers and introduced
on April 2, 1987. Features include a 16- or 32-bit
bus width and multiple master control. By allowing
several processors to arbitrate for resources
on a single bus, the MCA is optimized for multitasking,
multiprocessor systems. Offers switchless configuration
of adapters, which eliminates one of the biggest
headaches of installing older adapters.
MCE - Machine Check Detection. A function
supplied the Intel Pentium processor that executes
error detection of internal devices and the external
bus interface. Exceptions are generated for a
variety of conditions when the MCE bit in CR4
MCD - Multimedia Cartridge Drive.
MCGA - MultiColor Graphics Array. A
type of PC video display circuit introduced by
IBM on April 2, 1987, that supports text and graphics.
Text is supported at a maximum resolution of 8Ox25
characters in 16 colors with a character box of
8xl6 pixels. Graphics is supported at a maximum
resolution of 32Ox2OO pixels in 256 (from a palette
of 262,144) colors or 64Ox480 pixels in 2 colors.
The MCGA outputs an analog signal with a horizontal
scanning frequency of 31.SKHz, and supports analog
color or analog monochrome displays.
MCM - Multichip Module. A single IC package
that contains two or more individual die.
MDA - Monochrome Display Adapter. A type
of PC video display adapter introduced by IBM
on August 12, 1981, that supports text only. Text
is supported at a maximum resolution of 80x25
characters in four colors with a character box
of 9xl4 pixels. Colors, in this case, indicate
black, white, bright white, and underlined. Graphics
modes are not supported. The MDA outputs a digital
signal with a horizontal scanning frequency of
18.432 KHz, and supports TTL monochrome displays.
The IBM MDA also included a parallel printer port.
MFM - Modified Frequency Modulation. Common
technique used to encode the magnetic fluxes recorded
on a drive into data. Still used on floppy drives
and most XT and AT systems. Notice that most drive
types supported in CMOS have 17 sectors per track.
This is the standard density for MFM encoding.
encoding data as a series of magnetic flux reversals
on disk or tape, commonly knownas double-density
recording. In contrast to FM, modified frequency
modulation omits all clock pulses except those
between pairs ofzero bits. See also FM and
MHz An abbreviation for megahertz, a unit
of measurement indicating the frequency of one
million cycles per second. One hertz (Hz) is equal
to one cycle per second. Named after Heinrich
R. Hertz, a German physicist who first detected
electromagnetic waves in 1883.
MIDI - Musical Instrument Digital Interface.
An interface and file format standard for connecting
a musical instrument to a microcomputer and storing
musical instrument data. Multiple musical instruments
can be daisy-chained and played simultaneously
with the help of the computer and related software.
The various operations of the instruments can
be captured saved, edited, and played back. A
MIDI file contains note information, timing (how
long a note is held), volume, and instrument type
for as many as 16 channels. Sequencer programs
are used to control MIDI functions such as recording,
playback, and editing. MIDI files store only note
instructions and not actual sound data.
MI/MIC - Mode Indicate/Mode Indicate Common.
also called forced or manual originate. Provided
for installations in which equipment other than
the modem does the dialing. In such installations,
the modem operates in dumb mode (no auto-dial
capability), yet must go off-hook in originate
mode to connect with answering modems.
MIPS - Million Instructions Per Second.
Refers to the average number of machine-language
instructions a computer can perform or execute
in one second. Because different processors can
perform different functions in a single instruction,
MIPS should be used only as a general measure
of performance among different types of computers.
MMU - Memory Management Unit. A chip or
circuit that translates virtual memory addresses
to physical addresses and may implement memory
MMX - Multi Media Extension. A set of multimedia
oriented x86 instructions that Intel is adding
to versions of the Pentium and other processors.
SIMD (Single Instruction Multiple Data)
is the basis for Intel's new MMX technology
that allows many pieces of information to be processed
with a single instruction, providing parallelism
that greatly increases performance.
MO - Magneto-Optical. MO drives utilize
both magnetic and optical storage properties.
MO technology is erasable and recordable, as opposed
to CD-ROM (Read-Only) and WORM (Write-Once) drives.
MO uses laser and magnetic field technology to
record and erase data. The laser is used to heat
an area on the disk, which can then be recorded
magnetically. MO drives are most commonly used
in removable storage applications.
MOS - Metal-Oxide Semiconductor. Refers
to the three layers used in forming the gate structure
of a field-effect transistor (FET). MOS circuits
offer low-power dissipation and enable Transistors
to be jammed close together before a critical
heat problem arises. PMOS, the oldest ,type of
MOS circuit, is a silicon-gate P-channel MOS process
that uses currents made up of positive charges.
NMOS is a silicon-gate N-channel MOS process that
uses currents made up of negative charges and
is at least twice as fast as PMOS. CMOS, Complementary
MOS, is nearly immune to noise, runs off almost
any power supply, and is an extremely low-power
MP - Multiprocessor. A system with more
than one processor typically sued to refer to
systems with more than one central processor.
MPP - Massively Parallel Processor. A machine
that contains many processors, each with its own
memory and optional I/O ports. This is know as
independent processor architecture. Each processor
runs its own operating system's code and is linked
to all other processors through some form of interconnection
fabric. This independent processor architecture
is much more difficult to program than an SMP
system, but it is easier to scale to large sizes.
MPPs with more than 1,000 processors have been
MTBF - Mean Time Between Failures. Reliability
rating indicating the expected failure rate of
a product (hard drive) in power on hours (POH).
Since manufacturers differ in the ways they determine
the MTFB, comparisons of products should always
take into account the MTBF calculation method.
MTTR - Mean Time To Repair. The average
time it takes to repair a drive that has failed
for some reason. This only takes into consideration
the changing of the major subassemblies such as
the circuit board or sealed housing. Component
level repair is not included in this number as
this type of repair cannot be performed in the
MTF - Modulation Transfer Function. The
ration of contrast to maximum usable brightness.
The MTF should be greater than 35%.
MX - The Intel Triton II motherboard chip.
The MX supports DIMMs.
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Compiled by Scott
McArdle, MagnaCom Limited. I hope this list
has helped you and if there is an item that should
be on this list, please let me know. Thanks. PS,
I've spent 100's of hours maintaining this list,
please don't be a LAMER.