Experiment :- 15
Study and comparison of
various types of Memory
Types of Computer Memory: RAM, ROM and
Secondary Memory
What is computer memory?
Computer memory is a data storage technology that is capable of storing or
saving data, temporarily or permanently. The data stored are in a binary form
such as 0 and 1 as well, allowing the user to save and retrieve the information
anytime they require it.
Why is computer memory so important?
You can imagine computer memory to be a human brain, a computer memory
provides the computer space to access data quickly. This would then allow the
processor to communicate with the program much quicker. Without computer
memory, the user wouldn’t be able to save anything as well, which makes it
incredibly important!
How does computer memory work?
To understand how computer memory work, take a look at this hierarchy:
Main categories of computer memory
After talking about how computer memory is important, we did mention briefly
about RAM and ROM earlier, but do you know there are a lot more sub-
categories of it?
What will be covered:
Primary Memory
RAM: SRAM, DRAM
ROM: MROM, PROM, EPROM, EEPROM
Secondary Memory
SDD: SATA, PCIe, M.2, U.2, NVMe
HDD
Flash Drives
NAS
SAN
Cloud Storage (tertiary memory)
Overview of Primary Memory
What is Primary Memory?
The main memory in a computer, also known as internal memory or internal
storage. Accessing data from primary memory is pretty fast and it is either
volatile like RAM or non-volatile like ROM. The capacity of primary memory is
also limited and generally smaller when compared to secondary memory.
RAM: Random-access memory
RAM is the main memory in a computer system, also known as cache memory. It
is basically a high-speed component that temporarily stores the device needs,
and allow the device to access the data immediately.
SRAM: Static RAM
SRAM is a type of semiconductor memory and it uses bistable latching circuitry
to store each bit, this makes it very fast and thus the name cache memory.
DRAM: Dynamic RAM
DRAM is another type of RAM that stores each bit of data in a separate capacitor
within an integrated circuit.
The main difference between SRAM and DRAM:
ROM: Read Only Memory
ROM is also a primary memory just like RAM, but unlike RAM, ROM is able to
store data permanently which makes it non-volatile. It is a programmable chip
that stores all the most important instructions required to start the system, this
process is also known as bootstrap.
Alike to RAM, there are a few different types of ROM:
MROM: Mask ROM
MROM is a hand-wired device, one of the first ROMs.
PROM: Programmable ROM
PROM is as its name states, a read only memory chip that only allows the user to
overwrite the data once.
Now that we’ve talked all about primary memory, let’s do a tiny recap and look
at RAM and ROM’s differences:
Overview of Secondary Memory
What is the Secondary Memory?
The secondary memory is also known as external memory or auxiliary memory.
Unlike primary memory, secondary memory is generally volatile and they tend
to process data slower than primary memory. The secondary is comparably less
important than primary memory since they’re basically extra storage for more
data.
SSD: Solid-State Drive
SSD uses a simple memory chip called NAND flash memory, and it is a newer
kind of storage devices used in computers, meant to replace HDDs (we’ll
address this later). SSDs are able to speed up your computer which could
improve the overall performance.
SATA: Serial Advanced Technology Attachment
SATA SSDs are pretty common and they are a type of interface connection that
allows SSDs to communicate data with the system.
PCIe: Peripheral Component Interconnect Express
PCIe, also abbreviated as PCI Express, is a solid-state drive connected to a
computer system using a PCIe interface.
M.2
M.2 SSD was previously known as NGFF (Next Generation Form Factor), which
contains flash memory and controller chips.
U.2
U.2 SSD is previously known as SFF-8639, an interface that is defined as SSD
Form Factor Working Group (SFFWG).
HDD: Hard Disk Drive
HDD is a traditional storage device, also known as magnetic storage devices,
where the data is stored using a magnetized medium.
To help you visualise how an HDD’s moving parts look like, here’s a labelled
diagram of it:
Flash Drives
Flash drives are also known as thumb drives, pen drives and sometimes USB
drives, it is also one of the most popular secondary storage devices.
NAS: Network-Attached Storage
NAS is a type of storage network, it is basically a specialised file server.
SAN: Storage Area Network
SAN is also another type of storage network, similar to NAS, SAN takes storage
devices away from the server to create a central pool of data.
Secondary Memory: SSD vs HDD, NAS
vs SAN
Now that we’ve talked about secondary memory, let’s first compare the
difference between SSD and HDD:
SSD HDD
Price Very pricy Affordable
Access
Much faster than HDD Pretty fast as well but slower than SSD
Time
No movable parts, thus its much more Consists of different movable parts, thus it is more
Reliability
reliable prone to errors
Low power consumption as compared
Power HDD requires more power to move the different parts
to HDD
Generates a lot of heat which causes damage to the
Heat Less heat is generated
parts overtime
Next up, NAS vs SAN:
Primary vs Secondary Memory
After talking about primary and secondary memory in detail, let’s finally look at
their differences to help you understand better:
Primary Memory Secondary Memory
Can be volatile (RAM) and non-volatile
Nature Non-volatile
(ROM)
Alias Internal memory Auxiliary memory
Typically more pricy than secondary
Price Cheaper than primary memory
memory
Accessed indirectly, need to be transferred to the primary memory
Access Accessed directly by processing unit
accessed by CPU
Accesses Accessed by the data bus Accessed by I/O channels
FormationVolatile memory won’t retain data Non-volatile memory will be able to retain data
Usually smaller storage than secondary
Capacity Has much more power to store data
memory
