- 1.a broad term used to refer to a series of dynamic random
access memory integrated circuits modules mounted on a printed
circuit board and designed for use in personal computers,
workstations and servers. A memory module is the computer part that
holds the Random Access Memory (RAM), measured in megabytes or
gigabytes. a megabyte being 1,000,000 bytes of storage, and a
Gigabyte being 10,000,000,000 bytes of storage. All of these bytes
are placed in small circuits on a memory module stick, making it
easy for anyone to replace or add more RAM as the computer needs
it.
2. Types of Memory Module Dual in-line package memory SIPP
memory, single in-line pin package memory SIMM, a single in-line
memory module DIMM, dual in-line memory module SO-DIMM SDR SDRAM
DDR, DDR2, DDR3 SDRAM TransFlash Memory Module 3. DIP dual in-line
package (DIP or DIL) is an electronic device package with a
rectangular housing and two parallel rows of electrical connecting
pins. 2 parallel connecting pins socket circuit board 4. SIPP
single in-line pin package was a type of random access memory. It
consisted of a small printed circuit board upon which were mounted
a number of memory chips. It had 30 pins along one edge which mated
with matching holes in the motherboard of the computer. This type
of memory was used in 80286 and some 80386 systems. It was later
replaced by SIMMs, which proved to be easier to install. 5. SIMM
single in-line memory module, is a type of memory module containing
random access memory used in computers from the early 1980s to the
late 1990s. It differs from a dual in-line memory module (DIMM),
the most predominant form of memory module today, in that the
contacts on a SIMM are redundant on both sides of the module. 6.
SIMM 30- (top) and 72-pin (bottom) SIMMs. Early 30-pin modules
commonly had either 256 KB or 1 MB of memory. 7. SIMM The first
variant of SIMMs has 30 pins and provides 8 bits of data. They were
used in AT (286), 386, 486, Macintosh Plus, Macintosh II, Quadra,
Atari STE and Wang VS systems. The second variant of SIMMs has 72
pins and provides 32 bits of data. These appeared first in the
early 1990s in the IBM PS/2, and later in systems based on the 486,
Pentium, Pentium Pro, early Pentium II. 8. SIMM 30-pin SIMM Memory
Module Pin # Name Signal Description Pin # Name Signal Description
1 VCC +5VDC 16 DQ4 Data 4 2 /CAS Column Address Strobe 17 A8
Address 8 3 DQ0 Data 0 18 A9 Address 9 4 A0 Address 0 19 A10
Address 10 5 A1 Address 1 20 DQ5 Data 5 6 DQ1 Data 1 21 /WE Write
Enable 7 A2 Address 2 22 VSS Ground 8 A3 Address 3 23 DQ6 Data 6 9
VSS Ground 24 A11 Address 11 10 DQ2 Data 2 25 DQ7 Data 7 11 A4
Address 4 26 QP* Data parity out 12 A5 Address 5 27 /RAS Row
Address Strobe 13 DQ3 Data 3 28 /CASP* Parity Column Address Strobe
14 A6 Address 6 29 DP* Data parity in 15 A7 Address 7 30 VCC +5VDC
9. DIMM dual in-line memory module, comprises a series of dynamic
random-access memory integrated circuits. These modules are mounted
on a printed circuit board and designed for use in personal
computers, workstations and servers. DIMMs began to replace SIMMs
(single in-line memory modules) as the predominant type of memory
module as Intel P5- based Pentium processors began to gain market
share. 10. DIMM While the contacts on SIMMs on both sides are
redundant, DIMMs have separate electrical contacts on each side of
the module. Another difference is that standard SIMMs have a 32-bit
data path, while standard DIMMs have a 64-bit data path. Since
Intel's Pentium many processors have a 64-bit bus width, requiring
SIMMs installed in matched pairs in order to populate the data bus.
The processor would then access the two SIMMs in parallel. DIMMs
were introduced to eliminate this practice. 11. DIMM Two types of
DIMMs: a 168-pin SDRAM module (top) and a 184-pin DDR SDRAM module
(bottom). Note that the SDRAM module has two notches on the bottom
edge, while the DDR1 SDRAM module has only one. 12. SO DIMM small
outline dual in-line memory module, is a type of computer memory
built using integrated circuits. SO-DIMMs (also written SODIMMs)
are a smaller alternative to a DIMM, being roughly half the size of
regular DIMMs. SO- DIMMs are often used in systems which have space
restrictions such as notebooks, small footprint PCs (such as those
with a Mini-ITX motherboard), high-end upgradable office printers,
and networking hardware like routers. PC6400 DDR2 SO-DIMM (200
pins) PC3-10600 DDR3 SO-DIMM (204 pins) 13. Common Types of DIMM
72-pin SO-DIMM (not the same as a 72-pin SIMM), used for FPM DRAM
and EDO DRAM 100-pin DIMM, used for printer SDRAM 144-pin SO-DIMM,
used for SDR SDRAM 168-pin DIMM, used for SDR SDRAM (less
frequently for FPM/EDO DRAM in workstations/servers, may be 3.3 or
5 V) 172-pin MicroDIMM, used for DDR SDRAM 184-pin DIMM, used for
DDR SDRAM 200-pin SO-DIMM, used for DDR SDRAM and DDR2 SDRAM
204-pin SO-DIMM, used for DDR3 SDRAM 214-pin MicroDIMM, used for
DDR2 SDRAM 240-pin DIMM, used for DDR2 SDRAM, DDR3 SDRAM and
FB-DIMM DRAM 244-pin MiniDIMM, used for DDR2 SDRAM 14. 168-pin
SDRAM On the bottom edge of 168-pin DIMMs there are 2 notches, and
the location of each notch determines a particular feature of the
module. The first notch is DRAM key position. It represents RFU
(reserved future use), registered, and unbuffered (in that order
from left to middle to right position). The second notch is voltage
key position. It represents 5.0V, 3.3V, and Reserved 15. DDR SDRAM
Double data rate synchronous dynamic random- access memory (DDR
SDRAM) is a class of memory integrated circuits used in computers.
DDR SDRAM (sometimes referred to as DDR1 SDRAM) has been superseded
by DDR2 SDRAM and DDR3 SDRAM, neither of which is either forward or
backward compatible with DDR SDRAM, meaning that DDR2 or DDR3
memory modules will not work in DDR- equipped motherboards, and
vice versa. 16. CLOCK CYCLE & PREFETCH BUFFER Clock Cycle All
computers have an internal clock in the form of a chip containing a
crystal that vibrates at a consistent frequency when applied to
electricity. This frequency is knows as the clock rate. Each
vibration of the crystal represents one clock cycle. The clock
cycle is the shortest amount of time in which the computer can
execute an operation. The reliability of the clock rate allows for
the synchronization of computer activities, including those of RAM
and the computer's Central Processing Unit (CPU). Prefetch Buffer
RAM is, essentially, a bunch of electrical switches or
"transistors." Each transistor is attached to a capacitor, which is
capable of storing charge. A closed transistor blocks current,
leaving its capacitor empty, thus representing a "0." An open
transistor allows current to flow through, charging its capacitor
so it represents a "1." The transistors are situated into rows and
columns. In older versions of RAM, the computer would have to send
a different request each time it accessed data on a given row. A
prefetch buffer reads not only the data requested, but also data
adjacent to it on its row, thus providing the processor with more
of the "datawords" it needs per memory access. 17. Comparison of
Memory Module DIMM 18. DDR, DDR2 & DDR3 COMPARISON DDR DDR
stands for Double Data Rate. Like SDRAM, it operates at the rate of
the computer's clock cycle. However, unlike SDRAM, it can transfer
data twice per clock cycle. It does this by using the rising and
falling edges of the clock signal, also known as "double pumping"
and employing a prefetch buffer capable of accessing two datawords
at a time. This means that it can store and move a value in the
same amount of time it takes SDRAM to do one or the other,
effectively doubling the memory's speed. DDR2 DDR2 also utilizes
the same double pumping technique as DDR. It achieves performance
gains by using a prefetch buffer that retrieves four datawords per
memory access. This allows it to transfer data four times per clock
cycle (compared to twice in the case of DDR). Its improved
efficiency allows it to consume less power than DDR. DDR3 Like all
other forms of DDR, DDR3 transfers data twice per clock cycle.
However, its prefetch buffer can access eight datawords at a time.
Thus, it can transfer data eight times per clock cycle, giving it a
maximum data transfer rate twice that of DDR2 while using less
power. 19. TransFlash or SECURE DIGITAL is a non-volatile memory
card format for use in portable devices, such as mobile phones,
digital cameras, GPS navigation devices, and tablet computers. 20.
The Secure Digital format includes three card families available in
three different form factors. The three families are: 1. Original
Standard-Capacity (SDSC) 1MB to 2 GB (some 4GB) 2. High-Capacity
(SDHC) 4GB to 32 GB 3. eXtended-Capacity (SDXC) 32GB to 2TB The
three form factors are the original size, the "mini" size, and the
"micro" size TransFlash or SECURE DIGITAL 21. TransFlash or SECURE
DIGITAL 22. Memory Hierarchy The levels of memory in computer, from
fastest to slowest speed : 1. CPU 2. L1 Cache 3. L2 Cache 4. Main
Memory 5. Virtual Memory 6. Disk 23. CPU The central processing
unit is one of the most important components in the computer. It is
where various tasks are performed and an output is generated. When
the microprocessor completes the execution of a set of
instructions, and is ready to carry out the next task, it retrieves
the information it needs from RAM. Typically, the directions
include the address where the information, which needs to be read,
is located. The CPU transmits the address to the RAM's controller,
which goes through the process of locating the address and reading
the data. 24. Level 1 or L1 cache is special, very fast memory
built into the central processing unit (CPU) to help facilitate
computer performance. By loading frequently used bits of data into
L1 cache, the computer can process requests faster. Most computers
also have L2 and L3 cache, which are slower than L1 cache but
faster than Random Access Memory (RAM). While this is a good
strategy, the CPU can work faster than RAM, and to speed things
along, you might think of L1, L2 and L3 cache as the go-betweens
that anticipate what requests will be made of RAM, holding that
data at the ready. When a request comes, the CPU checks L1 cache
first, followed by L2 and L3 cache (if present). If the CPU finds
the requested data in cache, its a cache hit, and if not, its a
cache miss and RAM is searched next, followed by the hard drive.
The goal is to maximize hits and minimize misses that slow
performance. L1 CACHE 25. The main memory in a computer is called
Random Access Memory. It is also known as RAM. This is the part of
the computer that stores operating system software, software
applications and other information for the central processing unit
(CPU) to have fast and direct access when needed to perform tasks.
It is called "random access" because the CPU can go directly to any
section of main memory, and does not have go about the process in a
sequential order. RAM is one of the faster types of memory, and has
the capacity to allow data to be read and written. When the
computer is shut down, all of the content held in RAM is purged.
MAIN MEMORY 26. VIRTUAL MEMORY virtual memory is a memory
management technique developed for multitasking kernels. This
technique virtualizes the main storage available to a process or
task, as a contiguous address space which is unique to each running
process, or virtualizes the main storage available to all processes
or tasks on the system as a contiguous global address space. The
operating system manages virtual address spaces and the assignment
of real memory to virtual memory. 27. Permanent storage Permanent
storage is hard drives, (both internal and external) and Cd's DVDs
floppies + usb devices, including flash memory, because data that
is stored on these devices remain there until physically changed,
or deleted. The data is not lost when the power is turned off. 28.
Memory Hierarchy