RAM
RAM is short
for Random Access Memory. In common parlance, RAM refers to system memory, the
temporary storage area that holds all the data that the CPU is working on. All
data that requires processing by the CPU and the results of the processing are
first stored in the system memory.
RAM
pre se, refers to the type of storage medium
that allows any data stored within to be directly accessed without having
to access the preceding data (the latter
mode being called sequential access).
System memory
is volatile, which means that stored data is lost when the device is powered
down.
CAS
To be able to
access data from a particular storage area in RAM, the RAS and CAS procedures
are needed to provide the address of the storage area. The RAM is organized as
an array of storage areas. Each storage area can therefore be uniquely
identified by the number of the row and the number of the column that intersect
at that position. Row Access Storage (RAS) is the process of identifying the
row from which data needs to the process of identifying the column from which
data is to be accessed.
CAS LATENCY
Refers to the
delay between the CAS and the arriaval the arrival of the data from the RAM. It
is an indicator of the speed of the memory. And is expressed in the number of
clock cycles: a CAS Latency of 3 means that three clock cycles are needed after the CAS for data to
be produced by the RAM.
DDR SD RAM
Double Data
Rate SDRAM was an evolutionary improvement over SDRAM. It allowed data to be
transferred twice during every cycle. This effectively doubled the frequency of
the memory; DDR 266 memory actually works at 133 MHz. it is important to note
that the term is “DDR266 MHZ.”
Another mode
of notation is by referring to the peak data transfer speeds. So a DDR 266
module is also referred to as PC 2100, since it can transfer 2100 Megabytes per
second. DDR modules have 184 contacts, and are not backward-compatible.
DDR2 SD RAM
An evolution
of DDR SD RAM, DDR2 allows four data transfers per clock cycle, by clocking the
internal bus at twice the speed of
memory clock. Therefore the effective frequency of the momory becomes 4
times its actual frequency. A DDR2 800 module operates at 200 MHz. As in the
case of DDR SD RAM, the alternate notation relying to DDR2 400, a DDR2 module has 240 contacts, and is
not backward-com-patible.
DDR3 SD RAM
This is the
latest iteration of SDRAM, and increases the internal bus speed to 8 times the
memory clock, operating at 100 MHz and is also refered to as PC3 6400 DDR3 is
still a cutting-edge technology, and is supported by very few motherboard and
CPUs. DDR3 modules also have 240 pins, but they are keyed differently, so they
cannot be inserted into a DDR2 slot.
DIMM
Dual inline
Memory modules refers to the package in which RAM is available. Unlike the
earlier and now obsolete SIMM (Single Inline Memory Module), a DIMM has
contacts on both sides of the module.
DRAM
Dynamic RAM refers to volatile
RAM that is constantly refreshed to prevent stored contents from being lost.
All modern RAM is of this type, though there have been improvements. Data is
stored in the form of rows and columns, with each storage area in RAM having a
unique address that is a combination of the row and column number. DRAM was
available in different types like SDRAM, EDO
(Extended Data Out) RAM., FP (Fast Paging) RAM, and more, all of which are now
obsolete for SDRAM.
ECC RAM
An Error Correction Code (ECC) RAM
module is a special type of module that includes additional components to
verify the integrity of data stored in or transferred by system RAM. This is
needed in critical system that require high levels of data integrity, like
servers.
RAS to CAS Delay
This is the number of clock
cycles that intervene between the identification of the row with the RAS and
the start of launching the CAS. This is displayed as “tRCD” in the Bios.
RAS PRECHARGE TIME
This is the number of cycles that
are needed to refresh the RAS after the previous access before it can be used
for a new access.
RD RAM
RAMBUS Direct RAM was based on a
technology developed by RAMBUS. Unlike SDRAM, it used a serial mode of data
transfer and though the technology was considered superior to DDR, SDRAM, its
high cost made it unpopular. RDRAM modules are called RIMMs.
Registered RAM / Buffered RAM
This type of RAM module had additional storage areas-called
buffers of registers-where the data is stored temporarily and checked for data
integrity before being transferred Similar in use to ECC, RAM, though using a
different method, this type of RAM is needed in servers. Which require high
levels of data integrity.
SD RAM
Synchronous Dynamic RAM was an
improved version of DRAM that synchronized all its functions to a single
frequency usually the system’s FSB frequency. The frequency refers to the rate
at which the RAM would perform an action, namely refreshing, reading, or
storing. SD RAM is available in various frequencies, with the fastest modules,
targeted at enthusiasts, which perform at higher frequencies, are also
available). SD RAM modules have 168
contacts. After the release of DDR SDRAM, the original SDRAM began to be
referred to as SDR SDRAM (Single Data Rate SDRAM).
0 Comments