Chapter 1

Upgrading Memory

Prepared by:

Khurram N. Shamsi

Random Access Memory

Random Access Memory (RAM) is a short-term memory.

It is also sometimes called as volatile memory.

Once the power is turned off, all information stored there is lost (not saved).

Types of RAM

There are generally two broad categories of random access memory: DRAM (Dynamic Random Access Module)

These are inexpensive. They are used essentially for the computer's main

memory. SRAM (Static Random Access Module)

these are fast and costly. SRAM memories are used in particular for the

processor's cache memory.

RAM module formats

There are many type of random access memory.

They exist in the form of memory modules that can be plugged into the mother board.

Early memories existed in the form of chips called DIP (Dual Inline Package).

Nowadays, memories generally exist in the form of modules, which are cards that can be plugged into connectors for this purpose.

RAM module formats

There are generally three types of RAM modules:

SIMM format (Single Inline Memory Module) DIMM format (Dual Inline Memory Module) RIMM format (Rambus Inline Memory Module)

also called RD-RAM or DRD-RAM

Single Inline Memory Module

These are printed circuit boards with one side equipped with memory chips.

There are two types of SIMM modules, according to the number of connectors:

SIMM modules with 30 connectors (used in first-generation PCs).

SIMM modules with 72 connectors (used on PCs from the 386DX to the first Pentiums).

Dual Inline Memory Module

These are 64-bit memories. DIMM modules have memory chips on both

sides of the printed circuit board. They have 84 connectors on each side, giving

them a total of 168 pins. These modules have a second notch to avoid

confusion.

Rambus Inline Memory Module

These are also called RD-RAM or DRD-RAM. These are 64-bit memories developed by Rambus. They have 184 pins. These modules have two locating notches to avoid

risk of confusion with the previous modules. Smaller modules known as SO RIMM (Small

Outline RIMM) have been designed for portable computers.

SO RIMM modules have only 160 pins.

DRAM PM

The DRAM (Dynamic RAM) is the most common type of memory at the start of this millennium.

These memories have access times of 60 ns.

DRAM FPM

To speed up access to the DRAM, there is a technique, known as paging.

It involves accessing data located in the same column by changing only the address of the row.

This is known as DRAM FPM (Fast Page Mode).

FPM achieves access times of around 70 to 80 nanoseconds for operating frequency between 25 and 33 Mhz.

DRAM EDO

DRAM EDO (Extended Data Out) was introduced in 1995.

The technique used with this type of memory involves addressing the next column while reading the data in a column.

This creates an overlap of access thus saving time on each cycle.

EDO memory access time is around 50 to 60 nanoseconds for operating frequency between 33 and 66 Mhz.

SDRAM

The SDRAM (Synchronous DRAM) was introduced in 1997.

It allows synchronized reading of data with the mother-board bus.

The SDRAM thus eliminates waiting times due to synchronization with the mother-board.

The SDRAM operates with frequency up to 150 Mhz.

It can achieve access times of around 10 ns.

DR-SDRAM (Rambus DRAM)

The DR-SDRAM (Direct Rambus DRAM) can transfer data to a 16-bit bus at frequency of 800Mhz.

This type of memory is synchronized with the bus clock to enhance data exchange.

However, the RAMBUS memory is a proprietary technology, meaning that any company wishing to produce RAM modules using this technology must pay royalties to both RAMBUS and Intel.

DDR-SDRAM

The DDR-SDRAM (Double Data Rate SDRAM) is based on the SDRAM technology.

It doubles the transfer rate of the SDRAM using the same frequency.

Standard DRAM memories use a method known as SDR (Single Data Rate) involving reading or writing a piece of data at each leading edge.

DDR-SDRAM

The DDR doubles the frequency of reading/writing, with a clock at the same frequency, by sending data to each leading edge and to each trailing edge.

DDR memories generally have a product name such as PCXXXX where "XXXX" represents the speed in Mo/s.

DDR2-SDRAM

DDR2 (or DDR-II) memory achieves speeds that are twice as high as those of the DDR with the same external frequency.

DDR2 memory in fact uses two separate channels for reading and writing, so that it is able to send or receive twice as much data as the DDR.

DDR2 also has more connectors than the classic DDR (240 for DDR2 compared with 184 for DDR).

Summary Table

The table below gives the equivalence between the mother-board frequency (FSB), the memory (RAM) frequency and its speed:

MemoryNameFrequency (RAM)Frequency (FSB)SpeedDDR200PC1600200 MHz100 MHz1.6 Go/sDDR266PC2100266 MHz133 MHz2.1 Go/sDDR333PC2700333 MHz166 MHz2.7 Go/sDDR400PC3200400 MHz200 MHz3.2 Go/sDDR433PC3500433 MHz217 MHz3.5 Go/sDDR466PC3700466 MHz233 MHz3.7 Go/sDDR500PC4000500 MHz250 MHz4 Go/sDDR533PC4200533 MHz266 MHz4.2 Go/sDDR538PC4300538 MHz269 MHz4.3 Go/sDDR550PC4400550 MHz275 MHz4.4 Go/sDDR2-400PC2-3200400 MHz100 MHz3.2 Go/sDDR2-533PC2-4300533 MHz133 MHz4.3 Go/sDDR2-667PC2-5300667 MHz167 MHz5.3 Go/sDDR2-675PC2-5400675 MHz172.5 MHz5.4 Go/sDDR2-800PC2-6400800 MHz200 MHz6.4 Go/s

Steps to Install RAM

1. Find out what type of RAM is required for your desktop computer.

2. Turn off the computer and unplug it from everything.

3. Open your computer case.

4. Locate the RAM slots on your motherboard.

5. If you have an extra empty slot, put the new RAM in that one.

Steps to Install RAM

6. Press gently but firmly until the clamps close completely.

7. Close the computer and reattach all of the cords to the computer, including the screen and power cord

8. If your computer runs faster, it worked!

9. As a last check, check the system settings to make sure the RAM is okay.

Suggested Websites

http://en.wikipedia.org/wiki/RAM

http://www.microsoft.com/athome/setup/

addmemory.aspx

http://www.wikihow.com/Install-RAM

http://computer.howstuffworks.com/ram.htm

http://computer.howstuffworks.com/computer-

memory.htm