A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
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T
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V
W
X
Y
Z
A
AGP
See
Advanced Graphics Port
AIMM
AGP inline
memory module (See Advanced Graphics Port)
Access
Time
A measurement of time in nanoseconds (ns) used
to indicate the speed of memory. Access time is a cycle that
begins the moment the CPU sends a request to memory and ends
the moment the CPU receives the data it requested. Memory
modules complete this process in as fast as 6ns for PC133mhz
memory while older modules can take up to 80ns or more.
Advanced Graphics Port
(Accelerated
Graphics Port) AGP technology creates dedicated, high-speed
port for the transmission of large blocks of high resolution
data between the PC's graphics controller and system memory.
AGP is actually a port, and not a bus, because it only serves
two devices (the processor and the video card) and is not
expandable. One of the great advantages of AGP is that it
isolates the video subsystem from the rest of the PC so there
isn't nearly as much signal competition over I/O bandwidth as
there is across the PCI.
Asynchronous
Cache
Describes a type of L2 cache that is not in
synch with the system clock. Asynchronous cache is slower than
its synchronous counterpart, but is capable of delivering
information to the CPU at a rate 10 percent faster than
standard DRAM. Asynchronous cache was first used to boost
memory performance in 386 systems and is still widely used
today.
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B
BEDO
(Burst
EDO) DRAM -- a type of EDO DRAM that can process four memory
addresses in one burst. Unlike SDRAM, however, BEDO DRAM can
only stay synchronised with the CPU clock for short periods
(bursts) and it can't keep up with processors whose buses run
faster than 66 MHz. Burst EDO is a variant on EDO DRAM in
which read or write cycles are batched in bursts of four.
Burst EDO bus speeds range from 40MHz to 66MHz, as opposed to
the 33MHz bus speeds that can be accomplished using fast page
mode or EDO DRAM.
BGA
See Ball Grid
Array
Binary
A method of encoding
numbers as a series of bits. The binary number system, also
referred to as base 2, uses combinations of only two digits -
1 and 0.
Bit
Short for binary digit, the
smallest unit of data that can be processed or stored by a
computer. A bit can have a value of either 1 or 0. Bits make
up 'computer' language the same way letters of an alphabet
make up human languages. Different combinations of different
bits form 'words' and 'sentences' (actually signals) that a
computer understands. Before these words and sentences can be
transmitted from the CPU to memory, or vice versa, they must
be broken down into 8-bit segments called bytes. Older
computers were designed to handle only 8-bit data segments,
while newer models have progressed to 64-bit segments. This
larger bit width capacity generally means better and faster
computer performance.
BIOS
(Basic
Input/Output System) The BIOS is embedded software that
permits a computer to perform various functions without
accessing code from a hard drive or other peripheral memory.
The BIOS is a main link between a computer's hardware and
software.
Ball Grid Array
(Ball Grid
Array) BGA is a surface-mount integrated circuit package in
which the die is attached to the printed circuit board with
either plastic or ceramic solder balls instead of metal leads
that are used in other packaging. BGAs offer superior
electrical and thermal performance and have a smaller
footprint than leaded packages.
Bank
The
region on a motherboard where the slots for memory modules are
located. Memory banks are generally double-sided to
accommodate single or doubled-sided memory modules.
Block
A collection of data information
held on a storage device. The amount of data a block contains
is usually measured in bytes.
Buffered
Memory
Buffered means adding logic, particularly
drivers, to a SIMM or DIMM to increase the output current.
Buffering is used to overcome signal attenuation due to
capacitive loading. Modules that are "buffered" usually have
small buffer chips mounted on them.
Burn-in
The process of exercising an
integrated circuit at elevated voltage and temperature. This
process accelerates failures normally seen as "infant
mortality" in a chip. (Those chips that would fail early
during actual usage will fail during burn-in. Those that pass
have a life expectancy much greater than that required for
normal usage.)
Burst Mode
Bursting is a
rapid data-transfer technique that automatically generates a
block of data (a series of consecutive addresses) every time
the processor requests a single address. The assumption is
that the next data-address the processor will request will be
sequential to the previous one. Bursting can be applied both
to read operations (from memory) and write operations (to
memory).
Bus
The central communication
avenue in a PCs system board. It normally consists of a set of
parallel wires or signal traces that connect the CPU, the
memory, all input/output devices, and peripherals and allows
data to be transferred from one system component to another.
Busses come in a variety of bit widths and speeds. To prevent
data bottlenecks, the components attached to a bus must
operate at close to the same speed as the bus.
Byte
A unit of information made up of 8
bits. The byte is the fundamental unit of computer processing;
almost all aspects of a computer's performance and
specifications are measured in bytes or multiples of bytes
such as kilobytes (~1,000 bytes) or megabytes (~1 million
bytes), or gigabytes (~ 1 billion bytes)
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C
Cache
Controller
The circuit in control of the interface
between the CPU, cache and DRAM (main memory).
Cache memory
Cache RAM is high-speed
memory (usually SRAM) which is dedicated to storing frequently
requested data. If the CPU needs data, it will check in the
high-speed cache memory first before looking in the slower
main memory. Cache memory may be three to five times faster
than system DRAM. Most computers have two separate memory
caches; L1 cache, located on the CPU, and L2 cache, located
between the CPU and DRAM. L1 cache is faster than L2, and is
the first place the CPU looks for its data. If data is not
found in L1 cache, the search continues with L2 cache, and
then on to DRAM.
Card Memory
A type of
memory typically used in laptop and notebook computers. Credit
card memory features a small for factor and is named for its
similarity to the size of credit card.
CAS
(Column Address Select/or Strobe)--A
control pin on a DRAM used to and activate a column address.
The column selected on a DRAM is determined by the data
present at the address pins when CAS becomes active
CAS-B4-RAS (CBR)
(CAS Before RAS)- a
fast refresh technique in which the DRAM keeps track of the
next row it needs to refresh, thus simplifying what a system
would have to do to refresh the part. CAS before RAS. Column
address strobe before row address strobe.
CAS
Latency
The ratio between column access time and
clock cycle time. CAS Latency 2 (CL2) offers a slight
performance increase over CAS Latency 3 (CL3).
Check Bits
Extra data bits provided by a
DRAM module to support ECC function. For a 4-byte bus, 7 or 8
check bits are needed to implement ECC, resulting in a total
bus width of 39 or 40 bits. On an 8-byte bus, 8 additional
bits are required, resulting in a bus width of 72 bits.
Checkboard
A detail test pattern
designed to exercise each individual cell in the memory and
find possible shorts between adjacent columns and data buses
Clock
An electrical current that
alternates between high and low voltages. The speed of the
clock is measured in Megahertz (MHz)
Clock
Speed
The rate at which a computer's internal
system clock operates. The clock is used to synchronize
operations between the components within the clock.
CMOS
Complementary Metal Oxide
Semiconductor: a process that uses both N- and P-channel
devices in a complimentary fashion to achieve small geometries
and low power consumption.
COAST
(Cache
on a Stick) COAST is a module with SRAM chips that is placed
in the CELP socket on the motherboard to upgrade the
computer's L2 cache.
CPU
(Central
Processing Unit)--The chip in a computer that has primary
responsibility for interpreting commands and running programs.
The CPU is the most vital component of a computer system. The
speed of the CPU has a significant impact on overall system
performance, but the CPU doesn't act alone. If slower memory
is paired with a fast processor, the processor will be forced
to wait for the memory to respond. When the speed mismatch is
extreme, the user will see numerous memory errors and even
complete system failure.
C-RIMMTM
See
Continuity RIMMTM
CSP
See Chip Scale
Package.
Chip Set
A group of integrated
circuits designed to carry out one or more related functions
of a computer system. For example, one chipset may control the
flow of peripheral memory while another governs the system's
CPU functions for the system.
Contacts
See Edge Contacts
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D
DDR
(Double
Data Rate) or DDR SDRAM The next generation of the current
SDRAM. DDR finds its foundations on the same design core of
SDRAM, yet adds advances to enhance its speed capabilities. As
a result, DDR allows data to be read on both the rising and
the falling edge of the clock, delivering twice the bandwidth
of standard SDRAMS. DDR essentially doubles the memory speed
from SDRAMs without increasing the clock frequency.
DIMM
(Dual In-line Memory Module) A
printed circuit board with gold or tin/lead contacts and
memory devices. A DIMM is similar to a SIMM, but with this
primary difference: unlike the leads on either side of a SIMM,
which are "tied together" electrically, the leads on either
side of a DIMM are electrically independent, ie actually
separate circuits which allows for wider and faster data
transfer.
DRAM
(Dynamic Random Access
Memory) DRAM is the most common type of memory and is
"dynamic" because in order for the memory chip to retain data,
it must be refreshed constantly (every few milliseconds). If
the cell is not refreshed, the data is lost. DRAM temporarily
stores data in a cell composed of a capacitor and a
transistor. Each cell contains a specified number of bits.
These cells are accessed by row addresses and column
addresses.
DRDRAM
(Direct Rambus DRAM)--
a totally new RAM architecture, complete with bus mastering
(the Rambus Channel Master) and a new pathway (the Rambus
Channel) between memory devices (the Rambus Channel Slaves). A
single Rambus Channel has the potential to reach 500MBps in
burst mode; a 20-fold increase over DRAM.
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E
ECC
(Error
Checking/ Correcting Code) A method used to check the
integrity of data stored in memory . ECC memory improves data
integrity by detecting errors in memory and is more advanced
than parity because it can detect both multiple-bit errors and
single-bit errors (parity only detects single-bit errors). ECC
is typically found in high-end PCs and file servers where data
integrity is key. An ECC scheme capability is partially
determined by the sophistication of the "systematic code"
employed. The systematic code is like a reference table that
the memory system uses to determine whether or not the memory
has returned the correct data. Every time data is stored in
memory, this code is responsible for the generation of check
bits which are stored along with the data. When the contents
of a memory location is referenced, the ECC memory logic uses
the check bit information and the data itself to generate a
series of "syndrome bits". If these syndrome bits are all
zeros, then the data is valid and operation continues. If any
bits are ones, then the data has an error and the ECC memory
logic isolates the errors and reports them in the operating
system. In the case of a correctable error, the ECC memory
scheme can detect single and double bit errors and correct
single bit errors.
EDO
(Extended Data
Out) EDO RAM is similar to FPM memory, a form of DRAM
technology that shortens the read cycle between memory and
CPU. but provides improved performance by keeping available
data longer in memory. It eliminates much of the wait time by
allowing the processor to access data during the refresh
cycle. In other words, the computer can load data as it is
searching for new information. EDO memory is generally 10 to
20% faster than FPM memory. A computer must support EDO memory
in order to notice an increase in performance.
EDO
Parity RAM
EDO Parity RAM offers the high
performance of EDO memory and has built-in parity which
greatly improves reliability. Ideal for high-end PCs and
entry-level servers, EDO Parity modules are compatible with
any system that accepts a standard 72-pin EDO module and are
rapidly becoming the new standard on high-end systems.
Edge Contacts
See Edge Connector
Edge Connector
A row of metallic fingers
on the edge of a printed circuit board (PCB) that is inserted
in the appropriate socket on a motherboard. The edge connector
on a memory module provides the electrical connection that
allows it to communicate with the system.
EOS
(ECC on SIMM) A data-integrity
checking technology designed by IBM that features ECC
data-integrity checking built onto a SIMM.
EPROM
Erasable Programmable Read Only
Memory
Ethernet
A local-area network
(LAN) architecture that enables data transfer rates of 10 Mbps
and can transmit simultaneous demands while transferring data
between several computers.
Even
Parity
Even parity and odd parity are two different
parity protocols used to check the integrity of data stored in
memory. A memory manufacturer can use either protocol in a
memory product. Even parity adds an additional bit to every
byte of data to make the total number of 1's in the segment
even. When the byte passes to the CPU, the parity circuit
checks the byte to be sure it is still even. If it is, the
data is considered to be valid and the parity bit is removed
from the byte. If instead it registers as odd, it is
considered to be invalid and a parity error is generated.
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F
Fake
Parity
Unlike odd and even parity, fake parity is
not capable of detecting an invalid data bit. It was designed
to artificially 'satisfy' a parity-enabled computer without
actually checking the data for errors. Fake parity attaches a
bit to each byte of data just like odd and even parity
protocols. The difference is that fake parity simply adds the
correct parity bit as the data is sent to the CPU instead of
attaching it before the data is stored to memory, and
recalculating it before the byte passes to the CPU.
FSB
See Front Side Bus.
Flash
Memory
Flash memory is a non-volatile memory device
that retains its data when the power is removed. The device is
similar to EPROM with the exception that it can be
electrically erased, whereas an EPROM must be exposed to
ultra-violet light to erase.Flash memory does not need a
constant power supply to retain its data and it offers
extremely fast access times, low power consumption, and
relative immunity to severe shock or vibration. These
qualities combined with its compact size, make it perfect for
portable devices like scanners digital cameras, cell phones,
pagers, handhelds and printers. Flash chips have a lifespan
limited to 100,000 write cycles, which means flash will never
replace main memory in computers.
FPM
(Fast-Page Mode) A common DRAM
data-access scheme. Accessing DRAM is similar to finding
information in a book. First, you turn to a particular page,
then you select information from the page. Fast-page mode
enables the CPU to access new data in half the normal access
time, as long as it is on the same page as the previous
request.
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G
Gb
(see
gigabit)
GB
(see gigabyte)
Gigabit
Abbreviated Gb. Approximately 1
billion bits: 1 bit x 1,024 (that is, 1,073,741,824 bits) Or
exactly 2^30 bits.
Gigabyte
Abbreviated
GB. A unit of measurement approximately equal to 1024
megabytes. Computer components process data in bytes or
multiples of bytes such as kilobytes (~1,000 bytes), megabytes
(~1 million bytes), and gigabytes (~ 1 billion bytes).
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H
HPM
Hyper page
mode, also known as EDO.
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I
I/O
Port
(Input/Output) The link (program or device)
that transfers data between a computer and various peripheral
devices. This traffic can take the form of in-put only, such
as keyboards and mouses, while printers are generally out-put
only.
IC
Integrated Circuit. An
electronic circuit-consisting of components and
connectors-contained on a semiconductor chip. Usually packaged
in a plastic or ceramic case with external connector pins.
Integrated Circuit.
(see IC)
IO Card
A PCB that interfaces between
the computer and our own interface board.
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J
JEDEC
Joint
Electron Device Engineering Council. An international body of
semiconductor manufacturers that establishes the industry
standards for memory operation, features, and packaging.
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K
Kilobit
Approximately one thousand bits:
1 bit x 210 (that is, 1,024 bits).
Kilobyte
(KB)
A unit of measurement approximately equal to
1024 bytes. Computer components process data in bytes or
multiples of bytes such as kilobytes (~1,000 bytes), megabytes
(~1 million bytes), and gigabytes (~ 1 billion bytes).
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L
L1 Cache
(L1
Cache)- Sometimes also known as primary or level 1 cache, is a
small amount of high-speed memory that resides on or very
close to the CPU. L1 Cache interacts with the CPU for most
frequently requested instructions and data.
L2
Cache
(L2 cache) A specialized memory unit that
enhances DRAM performance by providing the CPU with data at
speeds ten times faster than DRAM. L2 cache comprised of
Static RAM (SRAM), a high-speed RAM that does not need to be
refreshed to retain its data. Most computers have two
different memory caches; L1 cache, located on the CPU, and L2
cache, located between the CPU and DRAM. L1 cache is faster
than L2, and is the first place the CPU looks for its data. If
data is not found in L1 cache, the search continues.
Latency
The elapsed time while one
system component waits for output from another component.
Latency is usually measured in clock cycles.
Logic
Board
(see motherboard)
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M
MB
(see
Megabyte)
MHz
(megahertz) represents one
million cycles per second. The speed of microprocessors are
measured in MHz to determine how many instructions per second
it can execute.
MIPS
(million
instructions per second) Measures the amount of system
instructions that a computer can perform in one second. MIPS
ratings are rarely used to represent system performance due to
the fact that instruction execution times vary and a mere
count of them isn’t an accurate measure the speed and power of
a system.
MTBF
(Mean Time Between
Failures) the average time (usually measured in hours) a
particular device will operate before failing. MTBF ratings
indicate the sturdiness of hard disk drives and printers.
Megabit
(Abbreviated Mb.) Approximately
one million bits: 1 bit x 1,0242 (that is, 1,048,576 bits).
Megabyte
(Abbreviated MB.) (MB) A unit
of measurement approximately equal to 1 million bytes
(1,048,576 to be exact).
Megahertz
A
measurement of clock cycles in millions of cycles per second.
Memory
A Term commonly used to refer to
computer system's random access memory (see also RAM). The
term memory has also been used to refer to all types of
electronic data storage (see storage). A computer system's
memory is crucial to its operation; without memory, a computer
could not read programs or retain data. Memory stores data
electronically in memory cells contained in chips. The two
most common types of memory chips are DRAM and SRAM.
Memory Bank
A logical unit of memory in
a computer, the size of which is determined by the computer's
CPU. For example, a 32-bit CPU calls for memory banks that
provide 32 bits of information at a time.
Memory
Configuration
The amount of memory in an IC and how
it is accessed. Also, a code on the lot traveler used to
indicate the IC's memory configuration (e.g., 1M1 = 1 Meg x 1,
4M4 = 4 Meg x 4, etc.).
Motherboard
Also
known as logic board, main board, or system board; your
computer's main electronics board, which in most cases either
contains all CPU, memory, and I/0 functions, or has expansion
slots that support them.
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N
Nanosecond(ns)
One
billionth of a second. Memory data access times are measured
in nanoseconds. For example, memory access times for typical
30- and 72-pin SIMM modules range from 60 to 100 nanoseconds.
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O
Odd
Parity
Even parity and odd parity are two different
parity protocols used to check the integrity of data stored in
memory. A memory manufacturer can use either protocol in a
memory product. Odd parity adds an additional bit to every
byte of data to make the total number of 1s odd. When the byte
passes to the CPU, the parity circuit checks the byte to be
sure it is still odd. If it is, the data is considered to be
valid and the parity bit is stripped from the byte. If instead
it registers as even, it is considered to be invalid and a
parity error is generated.
Operating
system
The program software that regulates the
operation of a computer system. Operating systems perform
basic tasks such as input/output distribution, tracking files,
controlling peripheral devices, memory allocation, etc.
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P
Parity
A
quality control method that checks the integrity of data
stored in a computer's memory. Parity works by adding an extra
bit of data to each byte to make the total number of 1's
either odd or even An error is detected if the parity circuit
determines that this number has changed, indicating that some
of the data may have been lost or otherwise corrupted. Two
different parity protocols exist, even parity and odd parity.
Parity protocols are capable of detecting single bit errors
only. To enable multiple-bit error detection, manufacturers
must use a more advanced form of error checking called Error
Correcting Code (ECC). See also Fake Parity.
PCB
(Printed Circuit Board) A component
made up of layers of copper and fiberglass; the surface of a
PCB features a pattern of copper lines, or "traces," that
provide electrical connections for chips and other components
that mount on the surface of the PCB. Examples: motherboard,
SIMM, credit card memory, and so on.
PCMCIA
(Personal Computer Memory Card
International Association) A standard that allows
interchangeability of various computing components on the same
connector. The PCMCIA standard is designed to support input/
output devices, including memory, fax/modem, SCSI, and
networking products. Pipeline Burst Cache
A type
of synchronous cache that uses two techniques to minimise
processor wait states - a burst mode that pre-fetches memory
contents before they are requested, and pipelining so that one
memory value can be accessed in the cache at the same time
that another memory value is accessed in DRAM.
Populated Board
A PCB with components.
Power Down
To turn the system's power
OFF.
Power up
To turn the system's power
ON.
Primary Cache
Cache that is closest
to the processor: typically located inside the CPU chip. Can
be implemented either as a unified cache or as separate
sections for instructions and data. Also referred to as Level
1 cache or internal cache.
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Q
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R
RAM
(Random
Access Memory) A type of memory that can be written to and
read from in a nonlinear (random) manner. When an application
is opened. it is transferred from the hard drive to RAM where
it is more readily accessible. RAM enhances system performance
because it can process requests from the CPU more quickly than
the hard drive. The kind of RAM used in main memory on most
computers is Dynamic RAM (DRAM). DRAM stores data as
electronic signals. These signals must be constantly refreshed
to keep them from dissipating. The more RAM your computer has,
the more data it can store at one time and subsequently the
more efficiently your computer will operate. The data held in
RAM is lost when the computer is turned off. The term random
derives from the fact that the CPU can retrieve data from any
individual location, or address, within RAM.
RAS
Row Address Select (or Strobe): a
control pin on a DRAM used to latch and activate a row
address. The row selected on a DRAM is determined by the data
present at the address pins when RAS becomes active.
RIMM
A memory module trademarked by
Rambus that is used with RDRAM chips and has different pin
settings than a DIMM package.
Refresh
An
electrical process used to maintain data stored in DRAM. The
process of refreshing electrical cells on a DRAM component is
similar to that of recharging batteries. Different DRAM
components call for different refresh methods.
Refresh Rate
The speed at which DRAM is
refreshed. DRAM stores data as a series of electron charges in
individual cells. This data must be constantly recharged or
'refreshed' to keep the data from dissipating. The refresh
rate refers to the size of the data that must be recharged,
and is typically expressed in kilobytes (~1,000 bytes). Two
common refresh rates are 2K and 4K, with 2K being the faster
rate.
Registered Memory
Registers on a
memory module increase the reliability of high-speed data
access by storing the data for one clock cycle before
releasing it to the motherboard. Registered memory is
typically employed in servers and other mission-critical
systems where the proper management of data is exceptionally
important.
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S
SDR
See SDRAM
SDRAM
(Synchronous DRAM) A DRAM
technology that uses a clock to synchronize signal input and
output on a memory chip. The clock is coordinated with the CPU
clock so the timing of the memory chips and the timing of the
CPU are "in synch." The synchronization eliminates time delays
and allows for fast consecutive read and write capability,
thereby increasing the overall performance of the computer.
SDRAM has two separate memory banks that operate
simultaneously, while one bank prepares for access, the other
is being accessed. SDRAM allows the CPU to access memory
approximately 25 percent faster than EDO memory because it is
controlled by the system clock. SDRAMs can only be used in
computers designed for it and cannot be mixed with any other
type of memory. SDRAM can operate at 100MHz, 133Mhz and
features a burst mode that allows it to address blocks of
information instead of small data bits.
SIMM
(Single In-line Memory Module) A
memory package consisting of a number of DRAM chips on a small
printed circuit board. This board provides the connection
between multiple memory chips and the computer system. SIMMS
come in various pin configurations, the most common type
being: 30 pin and 72 pin. A 30 pin SIMM has a row of 30 tin or
gold pins long the bottom of the module which determine the
amount of data the module can handle. These pins connect to
only one memory chip as opposed to DIMMs which can connect to
multiple chips.
SIMM Socket
An
interconnect component mounted on the system board, or
motherboard, designed to hold a single SIMM.
SODIMM
(Small Outline Dual In-line
Memory Module) An enhanced version of a standard DIMM. The
small outline DIMM is about half the length of a typical
72-pin SIMM. This compact DIMM are used in mobile computing
devices. SO DIMMs come in a variety of pin sizes and can be
installed either singly to support 32-bit systems, or in pairs
to support 64-bit systems.
Soft Error
An
error caused by a temporary disruption of the memory cell
SOJ
(Small Outline J-lead) A common form
of surface-mount DRAM packaging. It is a rectangular package
with J-shaped leads on the two long sides of the device.
Serial Presence Detect
An EEPROM on
certain memory modules used to store and provide information
to the system using the module.
Static Random
Access Memory
(see SRAM)
SRAM
(Static RAM) SRAM is similar to
DRAM but does not constantly refresh. SRAM is faster and more
expensive than DRAM and is generally used for speed-critical
areas of the computer such as cache memory.
Synchronous Cache
A kind of L2 cache
that is synchronized with the CPU. This eliminates the lag
time created while the CPU waits for cache memory to fulfill
its requests. Synchronous cache is typically 3 to 5 percent
faster than asynchronous cache, and is a full 20 percent
faster than standard DRAM. See also Asynchronous Cache.
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T
TAG
The subset
of the CPU address bits used to compare the tag bits of the
cache directory to the main memory address being accessed.
TSOP
(Thin Small Outline Package) A type
of DRAM package that uses gullwing shaped leads on both sides.
TSOP DRAM mounts directly on the surface of the printed
circuit board. The advantage of the TSOP package is that it is
one-third the thickness of an SOJ package. TSOP components are
commonly used in small outline DIMM and credit card memory
applications.
Type
This number (x8, x9,
x32, x36, x64, x72, x80) refers to the bit depth of a module,
or to the size of the data path used to access the memory.
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U
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V
Vcc
Collector
Common Voltage.
Volatile Memory
Memory
that loses its contents when the power is turned off. A
computer's main memory, made up of dynamic RAM or static RAM
chips, loses its content immediately upon loss of power.
Contrast ROM, which is non-volatile memory.
VRAM
(Video RAM) VRAM has two separate
data ports. One is dedicated to updating the image on the
screen while the other one is used for changing the image data
stored in memory. This "dual-ported" design gives higher
performance than DRAM which cannot read and write
simultaneously but is more expensive.
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W
Write
Time
Time expended from the moment data is entered
for storage to the time it is actually stored in the memory
cell.
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X
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Y
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Z
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