Mbps
Megabits per second.
MBps
Megabytes per second.
MCA (Micro Channel
Architecture)
It is the internal system bus for adding new capabilities to
the computer such as a hard drive controllerboard. MCA slots
are used in many of IBM's PS/2 computer models and "clones"
from other manufacturers. These computers can have two hard
drives installed. Configure the drive with the fastest data
transfer rate as drive-C.
MCD or Multimedia CD drive
It reads 5-inch high density dual-layer CDs. Single-sided
CDs store 3.7GB, double-sided CDs store 7.4GB.
McCD Minichanger
Drive includes one CD-ROM mechanism and a platter that holds 6 to 18 disks.
MD (MiniDisc)
MD drives use magnetic field modulation (MFM); which, differs from the laser modulation (LM) of MO drives
MDRAM
Multibank Dynamic RAMchips combine several small, independent banks of mini-DRAM (Dynamic RAM) in a single chip. The banks are connected by an internal bus. A repeater connects the internal bus to the external bus which is a simple, low-power synchronous DRAM-like interface that may have a frequency between 75 MHz abd 200 MHz; much wider than an SDRAM's. Independent bank organization allows a row-access cycle for one bank to be started while another bank is executing a 32-bit read or write.
MDRAMs supports clock speeds of 100 and 125 MHz and a 1 GB-per-second bandwidth for graphic and video implementations. Its granularity supports a 2.25 MB frame buffer, the exact requirement for true color (1,024 x 768) applications. MDRAM's "granularity" reduces the size of predefined memory segments of 1 MB, 2 MB, or 4 MB increments. This permits segments to be as little as 0.25 MB.
Medium
A manufactured products of various consistencies, like paper, metal wire, plastic records, magnetic tapes, magnetic disks and compact disks--of various sizes and shapes--which are used to store information.
Recordable media may be single- or double-sided, single-or multi-layered. Electronic data can be recorded on the media through various processes. The read and write processes may be either exclusive or combined within the same device that uses the media.
Some media, such as a CD may have special surfaces (the front) on which words and/or images can be printed. Such labels do not affect the read/write processes of data recorded on the back (or bottom) side.
Metal-film (MF) resistors
They are referenced with the other resistors.
MFLOPS
Millions of Floating Point Operations per Second.
MFM
Modified Frequency Modulation is the standard for ST506/412-inter-faced drives. The newer encoding method, RLL (Run Length Limited), "RILL," provides greater capacity. The DOS standard is 512 bytes per sector, if you increase the number of sectors, you will increase the disk's capacity. In both ST506 and ESDI drives, the disk-platters spin at 3,600 revolutions per minute (rpm). ST506 drives, using the MFM data-encoding, have the typical 17 sectors per track.
Note: PC What's The Problem? includes drive installation, test, and repair suggestions.
MHz
Megahertz is a million cycles per second. It is used as a data transfer rate measurement.
Millisecond (ms)
A measure of time, one-thousandth of a second. In computers, it used to determine "access times" to data-storage media. The lower the number, the faster the access; e.g, 8ms is faster than 9ms.
Miniature ROM cards
Initially there were four competing designs which competed with low-cost ROM and expensive flash ROM for implementation in a variety of applications from PDAs to toys to ultraportable digital music players:
a) CompactFlash card. From SanDisk, it uses a parallel interface.
b) MiniCard. Developed by Intel, it has a parallel interface.
c) MMC. MultiMediaCard is a 37 x 45 x 1.4-mm removable storage cards from Siemens. They can store 16 or 64 Mbits of ROM. Using a serial interface, multiple MMCs can be stacked to increase capacity.
d) Solid State Floppy Disk Cards. From Toshiba, it uses a parallel interface.
MiniCard or MC
A "half-size" standard from Intel is a 33-by-38-by-3,5-mm minature card. It is not compatible with CF. Compatibility is a software issue. The MC has a double-row 60-contact interface that has both a 20-bit address bus and a 16-bit data bus which allow full random access to the stored data. The card's 3.3-V/59-V key notch is next to the interface's (larger) alignment notch. A write-protect mechansim prevents accidental writes.
MLR
Multichannel linear recording of data technique developed by Tandberg Data Inc. and used for storing data on TRavan QIC ("TR-QIC") tapes.
MO
Magnetic Optical disk-cartridge media cannot be damaged by read/write head crashes or accidental contact with magnetic fields, and therefore is nearly indestructable&emdash;and reuseable. MO cartridges use either a 5.25-inch disk or a 3.5-inch disk.
The 5.25-inch MO-disk cartridges are supported by drives from Maxoptix, Ricoh and Sony; the 3.5" MO-disk cartridge is used in drives from IBM, MOST, Ricoh, Sony and Teac. 5.25-inch MO drives use ISO-standard two-sided 650M optical-disk cartridges. (Only one 325M-side can be read at a time; you must remove, then reinsert the cartridge its bottom-side up for the additional capacity.) These drives support both 512 and 1024 byte sectors.
The 650 Megabyte cartridges can be swapped among drives from each manufacturer. Maxoptix's Tahiti II drives can format a 650 Megabyte cartridge for a total of 1.3 Gigabytes using its optional, proprietary, ZCAV format. PPM data-encoding method is used by other drives to store the same amoun of data.
3.5-inch MO drives use single-sided disk-cartridges which are essentially very high density (VHD) 3.5" floppy disks (twice the thickness of the standard 3.5" DS HD disks). These disks can store 128M of data. (Some drives double the capacity, providing 256M on proprietary cartridges.) Some incompatibilities exist among disk cartridges from different manufacturers. For DOS compatibility, disks support 512 byte sectors.
Unlike the high density floppy drives, many 3.5" MO cartridges are also backward compatible and can format, read and write the lower-capacity 3.5" floppy disks used by PCs (720K, 1.44M, and 2.88M) and MacOS systems (800K and 1.4M). Another reference: Floptical.
Modem Eliminator
Also known as a "Null Modem." It connects two computers by their serial interfaces, elminating the need for each to have a modem.
MNP
A network error-checking protocol that makes a statistical analysis of (addressed) packets (of 1s and 0s), and transmit them for analysis at the receiving end. It handles multi-bit errors, (as does Cyclical redundancy check, CRC and X.PC). For two modems to communicate, they must use the same error-checking protocol, if any. The more efficient the error-checking, the slower it works.
Mopier
Multiple Original Printers is a class of printers with specific enhancements to support the heavy loads of large networks of computers. These enhancements include: 16MB to 32MB of DRAM for onboard micros; hard drives (in the 500MB to 2GB range) with remote diagnostic and software upgrade options; the ability to store and later generate multiple original copies of large and complex documents; the capability to receive and send facsimile transmissions; and to support the scanning of documents for data-entry and transfer to the network.
MOSFET
Metal-oxide semiconductor FETs, are referenced with the other transistors.
MR
Magneto-resistive heads can store data at very high densities on magnetic disk and tape surfaces.
ms millisecond
A mesurement indication a thousandth of a second of time.
MultiRead compatible
A specification from OSTA (Optical Storage Technology Association) which certifies that a CD-ROM or DVD-ROM drive can read CD-RW and CD-R disks; as well as, UDF (Universal Disk Format) which is used in some CD-RW and DVD-ROM drives. Look for the logo when purchasing such these drives.
N¥hand Disk
From Iomega Corp., these disks measure 1.875 inches-square, incorporate floating read/write heads (like their Zip drives) and is designed as a 20MB floppy disk substitute for flash-memory cards. These standard interfaces for solid-state flash-memory data storage devices provide for proper power up and power down sequencing via different pin lengths to ensure that hot insertion and removal of the card device&emdash;while the computer is powered on&emdash;will not result in card or computer damage or data loss.
Nanosecond (ns)
A measure of time, one-billionth of a second. In computers, it is used to determine DRAM, ASIC and CPU operation times. The lower the number, the faster the access; e.g, 7ns Static Cache RAM is faster than 80ns SIMM RAM.
NEXT
The near-end crosstalk, a cable specification of the interference that occurs adjacent to the connector at either end of a cable. NEXT is measured close to the source of the test signal.
Note: PC What's The Problem? includes functional cable troubleshooting suggestions.
NIC
Network Interface Card, an adapter card which lsts the computer it is installed appear as a node to a network.
NIC
Network Information Center, NIC is an organization responsible for supplying information for component networks that comprise the Internet.
NOC
Network Operations Center which is responsible for the day-to-day operations of the Internet's component networks.
Node
A device attached to a network. A node uses the network as a means of communication and has an address on the network.
NOISE
The electrical interference that affects a data signal moving through a cable. The interference can come from other wires inside the cable (crosstalk), or from external electrical devices, such as motors and fluorescent lights.
Normal Frequency
The midpoint in the passband, (a.k.a., Center Frequency).
NPN
These transistors are referenced with the other transistors.
NT
Label is used to indicate that a product os compatible with computers and software that use the Windows NT operating system.
Null Modem
Is referenced as a Modem Eliminator.
NUMA
Non Uniform Memory Access. A term used to describe architectures where different regions of memory have different access times.
NVP
The nominal velocity of propagation is the speed at which a signal flows through a cable, expressed as a fraction or percentage of the speed of light in a vacuum. Cable Testers use this value along with the amount of time it takes for a signal to reflect back to the tester, to calculate the length of a cable.
OEM
Designed for use by Original Equipment Manufacturer.
Ohm (½)
It is a unit of resistance. A thick copper wire might have, for example, a resistance of one thousand ohms (also known as kilo-ohms), represented as: 1k½. A thinner wire might have a greater resistance, for example, one million ohms; also known as mega-ohms, and represented as: 1M½.
Ohms law relates resistance to volts divided by amps; (1½ = 1V ÷ 1A). It relates volts to amperes multiplied by resistance; (1V = 1A x 1½). And it relates amperes (current) to volts divided by resistance; (1A = 1V ÷ 1½).
Making a wire thinner or longer will increase its resistance to electrical flow. Also, winding the wire around or surrounding it by a carbon-compound rod also will increase its resistance.
OPEN
A break in a cable wire or electrical circuit.
Operational-Amplifiers
Op-amps are electrical components with two inputs, a positive (+) and negative (&endash;). When the negative inverted input goes higher than the positive non-inverted input, the output goes low (near ground) When the positive input is higher than the negative input, the output goes high (near Vcc).
Optocoupler (or optisolator)
These sensors are referenced with the other transistors.
References are samples only. Each one is presented in greater detail in the
Technical Research Assistant for 2001
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