Al-kitab University ‫جامعة الكتاب االهلية‬

Collage of Engineering Technolog ‫كلية التقنية اهلندسية‬

Computer Technology Engineering ‫هندسة تقنيات احلاسوب‬

Report

Student preparation :- Ahmed Hosni Al-Saeed.

. ‫ احمد حسني السعيد‬-: ‫أعداد الطالب‬

Level :- First year evening .

Computer Engineering .

Subject :- Computer Fundamentals .

Professor :- Hanan M . Shukur .

Report about : Memory chips .

Year:- 2019-2020
Memory chips
Random-access memory (RAM ):- is a form of computer memory that can be
read and changed in any order, typically used to store working data and machine
code.[1][2] A random-access memory device allows data items to be read or written in
almost the same amount of time irrespective of the physical location of data inside the
memory. In contrast, with other direct-access data storage media such as hard disks, CD-
RWs, DVD-RWs and the older magnetic tapes and drum memory, the time required to
read and write data items varies significantly depending on their physical locations on the
recording medium, due to mechanical limitations such as media rotation speeds and arm
movement.

RAM contains multiplexing and demultiplexing circuitry, to connect the data lines to the
addressed storage for reading or writing the entry. Usually more than one bit of storage is
accessed by the same address, and RAM devices often have multiple data lines and are
said to be "8-bit" or "16-bit", etc. devices.

In today's technology, random-access memory takes the form of integrated circuit (IC)
chips with MOS (metal-oxide-semiconductor) memory cells. RAM is normally associated
with volatile types of memory (such as dynamic random-access
memory (DRAM) modules), where stored information is lost if power is removed,
although non-volatile RAM has also been developed.[3] Other types of non-volatile
memories exist that allow random access for read operations, but either do not allow write
operations or have other kinds of limitations on them. These include most types
of ROM and a type of flash memory called NOR-Flash.

1-SIMM (single in-line memory module)

SIMM 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

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SIMM are redundant on both sides of the module. SIMMs were standardised under the
JEDEC JESD-21C standard.

Most early PC motherboards (8088-based PCs, XTs, and early ATs) used socketed DIP
chips for DRAM. As computer memory capacities grew, memory modules were used to
save motherboard space and ease memory expansion. Instead of plugging in eight or nine
single DIP chips, only one additional memory module was needed to increase the memory
of the computer.

The are two types of SIMM

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1- 30-pin SIMMs
Standard sizes: 256 KB, 1 MB, 4 MB, 16 MB
30-pin SIMMS have 12 address lines, which can provide a total of 24 address bits. With an
8 bit data width, this leads to an absolute maximum capacity of 16 MB for both parity and
non-parity modules (the additional redundancy bit chip usually does not contribute to the
usable capacity).

2- 72-pin SIMMs
Standard sizes: 1 MB, 2 MB, 4 MB, 8 MB, 16 MB, 32 MB, 64 MB, 128 MB (the standard
also defines 3.3 V modules with additional address lines and up to 2 GB) With 12 address
lines, which can provide a total of 24 address bits, two ranks of chips, and 32 bit data
output, the absolute maximum capacity is 227 = 128 MB.

2-DIMM (dual in-line memory module)

DIMM 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.

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
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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 disadvantage.

Variants of DIMM slots support DDR, DDR2, DDR3 and DDR4 RAM.

168-pin SDRAM
On the bottom edge of 168-pin DIMMs there are two notches, and the location of each
notch determines a particular feature of the module. The first notch is the DRAM key
position, which represents RFU (reserved future use), registered, and unbuffered DIMM
types (left, middle and right position, respectively). The second notch is the voltage key
position, which represents 5.0 V, 3.3 V, and RFU DIMM types

difference between SIMM and DIMM

S.NO SIMM DIMM

1. In SIMM, Pins present in either facetDIMM
are pins are freelance.
connected.
2. SIMM supports 32 bit channel for DIMM
data supports 64 bit channel
transferring. for data transferring.

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 3. SIMM consumes 5 volts of power. DIMM consumes 3.3 volts of
power.
4. SIMM provides the storage 4 MB to 64 MB. DIMM provides the storage 32
MB to 1 GB.
5. The classic or most common pin configuration
Theof foremost common pin
the SIMM module is 72 pins. configuration of the DIMM
module is 168 pins.
6. SIMMs are the older technology. DIMMs are the replacement of
the SIMMs.
7. SIMMs are installed in pairs at a time. DIMMs are installed one at a
time.
8. SIMMs are used by 486 CPU as well as DIMMs
early are used by modern
Pentium computers. Pentium computers.
9. The length and width of SIMM are respectively
The length and width of DIMM
4.25 inches and 1 inch. are respectively 1.67 to 5.25
inches and 1 to 1.75 inches.
10. There are single notches in SIMMs. There are two notches in DIMMs.

Instruction cycle

The fundamental sequence of steps that a CPU performs. Also known as the "fetch-
execute cycle," it is the process whereby a single instruction is executed. The first half of
the cycle transfers the instruction from RAM to the instruction register (fetch) and decodes
it. The second half executes the instruction.

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 In a basic computer, each instruction cycle consists of the following phases:
1- Fetch instruction from memory.
2- Decode the instruction.
3- Read the effective address from memory.
4- Execute the instruction.

Fetch stage

The fetch step is the same for each instruction:

1- The CPU sends the contents of the PC to the MAR and sends a read command on the
address bus
2- In response to the read command (with address equal to PC), the memory returns the data
stored at the memory location indicated by PC on the data bus
3- The CPU copies the data from the data bus into its MDR (also known as MBR; see section
Role of components above)
4- A fraction of a second later, the CPU copies the data from the MDR to the instruction
register for instruction decoding
5- The PC is incremented so that it points to the next instruction. This step prepares the CPU
for the next cycle

Decode stage

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The decoding process allows the CPU to determine what instruction is to be performed so
that the CPU can tell how many operands it needs to fetch in order to perform the
instruction. The opcode fetched from the memory is decoded for the next steps and moved
to the appropriate registers. The decoding is done by the CPU's Control Unit.

Reading the effective address stage

This step evaluates which type of operation is to be performed. If it is a memory operation,

the computer checks whether it's a direct or indirect memory operation:

1-Direct memory operation - Nothing is done.

2-Indirect memory operation - The effective address is read from memory.

If it is an I/O or register instruction, the computer checks its type and executes the
instruction.

Execute stage

The function of the instruction is performed. If the instruction involves arithmetic or logic,
the ALU is utilized. This is the only stage of the instruction cycle that is useful from the
perspective of the end user. Everything else is overhead required to make the execute step
happen.

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References

1. ^ "RAM". Cambridge English Dictionary. Retrieved 11 July 2019.

2. ^ "RAM". Oxford Advanced Learner's Dictionary. Retrieved 11
July 2019.
3. ^ Gallagher, Sean (2013-04-04). "Memory that never forgets: non-
volatile DIMMs hit the market". Ars Technica. Archived from the
original on 2017-07-08.
4. ^ "IBM Archives -- FAQ's for Products and
Services". ibm.com. Archived from the original on 2012-10-23.
5. ^ Napper, Brian, Computer 50: The University of Manchester
Celebrates the Birth of the Modern Computer, archived from the
original on 4 May 2012, retrieved 26 May 2012
6. ^ Williams, F.C.; Kilburn, T. (Sep 1948), "Electronic Digital
Computers", Nature, 162 (4117):
487, Bibcode:1948Natur.162..487W, doi:10.1038/162487a0. Reprint
ed in The Origins of Digital Computers
7. ^