1.
Memory Organization
Yamini Sree

2.
Basics :
• The memory unit is an essential component in any digital computer since it is
needed for storing programs and data.
• The memory unit that communicates directly with the CPU is know as Main
Memory.
• Devices that provide backup storage is know as Auxiliary memory.
• A special very high speed memory called a Cache.

3.
Memory Hierarchy
• The Computer memory hierarchy looks like a pyramid structure which is used to
describe the differences among memory types. It separates the computer storage
based on hierarchy.
• In Memory Hierarchy the cost of memory, capacity is inversely proportional to
speed. Here the devices are arranged in a manner Fast to slow, that is form
register to Tertiary memory.
• Memory hierarchy is arranging different kinds of storage present on a computing
device based on speed of access. At the very top, the highest performing storage
is CPU registers which are the fastest to read and write to. Next is cache memory
followed by conventional DRAM memory, followed by disk storage with different
levels of performance including SSD, optical and magnetic disk drives.
• To bridge the processor memory performance gap, hardware designers are
increasingly relying on memory at the top of the memory hierarchy to close /
reduce the performance gap. This is done through increasingly larger cache
hierarchies (which can be accessed by processors much faster), reducing the
dependency on main memory which is slower.

4.
Memory Hierarchy in a computer
system:

5.
Difference Between RAM & ROM
RAM
• RAM is a volatile memory which
could store the data as long as the
power is supplied.
• Data stored in RAM can be
retrieved and altered.
• Used to store the data that has to
be currently processed by CPU
temporarily.
ROM
• ROM is a non-volatile memory
which could retain the data even
when power is turned off.
• Data stored in ROM can only be
read.
• It stores the instructions required
during bootstrap of the computer.

6.
RAM
• It is a high-speed memory.
• The CPU can access the data
stored on it.
• Large size with higher capacity,
with respect to ROM.
• Used in CPU Cache, Primary
memory.
• The data stored is easily
accessible.
• Costlier
• A RAM chip can store only a few
gigabytes (GB) of data.
ROM
• It is much slower than the RAM.
• The CPU can not access the data
stored on it unless the data is
stored in RAM.
• Small size with less capacity, with
respect to RAM
• Used in Firmware, Micro-
controllers.
• The data stored is not as easily
accessible as in RAM.
• Cost is cheaper than RAM.
• A ROM chip can store multiple
megabytes (MB) of data.

7.
Bootstrap loader :
• The ROM portion of main memory is needed for storing an initial program called
a Bootstrap loader.
• It is a program whose function is to start the computer software operating
when power is turned on .
• Since RAM is volatile, its contents are destroyed when power is turned off.
• The contents of ROM remain unchanged when power is turned off and on
again.

8.
Computer Start Up:
• The startup of computer consists of turning the power on and starting the
execution of an initial program.
RAM & ROM Chips:
• A RAM chip is better suited for communication with the CPU it has one or more
control inputs that select the chip only when needed.
• A ROM chip is organized externally in a similar manner . Since a ROM can only
read , the data bus can only be in output mode.

9.
RAM AND ROM CHIPS:

10.
Memory connection to cpu:

11.
Thank You
Yamini Sree