Computer
Memory
Computer Memory
• A memory is just like a human brain. It is used to store data and
instructions.
• Computer memory is the storage space in the computer, where data is
to be processed and instructions required for processing are stored.
• The memory is divided into large number of small parts called cells.
• Each location or cell has a unique address, which varies from zero to
memory size minus one.
Memory is primarily of three types
Cache Memory
Primary Memory/Main Memory
Secondary Memory
Cache Memory
• Cache memory is a very high speed semiconductor memory which can
speed up the CPU.
• It acts as a buffer between the CPU and the main memory.
• It is used to hold those parts of data and program which are most
frequently used by the CPU.
• The parts of data and programs are transferred from the disk to cache
memory by the operating system, from where the CPU can access them.
Advantages
Cache memory is faster than main memory.
It consumes less access time as compared to main memory.
It stores the program that can be executed within a short period of time.
It stores data for temporary use.
Disadvantages
Cache memory has limited capacity.
It is very expensive.
Cache Memory Size
L1 - 2MB
L2 - 8MB
L3 - 128MB
The L1 memory cache is typically 100 times faster than your RAM,
while the L2 cache is around 25 times faster.
Main Memory or RAM
These are semiconductor memories.
It is known as the main memory.
Usually volatile memory.
Data is lose in case power is switched off.
It is the working memory of the computer.
Faster than secondary memories.
A computer cannot run without the primary memory.
RAM
Random Access Memory
Two Main Types of RAM are:
Static RAM
Static RAM is the full form of SRAM.
In this type of RAM, data is stored using the state of a six transistor
memory cell.
Static RAM is mostly used as a cache memory for the processor (CPU).
Dynamic RAM
DRAM stands for Dynamic Random Access Memory.
It is a type of RAM which allows you to stores each bit of data in a
separate capacitor within a specific integrated circuit.
Dynamic RAM is a standard computer memory of the many modern
desktop computers.
RD RAM
Rambus Dynamic Random Access Memory is a full form of RDRAM.
This type of RAM chips works in parallel, which allows you to achieve
a data rate of 800 MHz or 1,600 Mbps.
It generates much more heat as they operate at such high speeds.
VRAM (Video)
• RAM optimized for video adapters is called VRAM.
• These chips have two ports so that video data can be written to chips at
the same time the video adapter regularly reads the memory to refresh
the monitor’s current display.
Flash Memory
• Flash memory is an electrically erasable and programmable permanent
type of memory. It uses a one-transistor memory to store a bit.
• It offers low power consumption and helps to reduce the cost. It is
mainly used in digital cameras, MP3 players, etc.
DDR SDRAM
• The full form of DDR SDRAM is Double Data Rate Synchronous
Dynamic Random-Access Memory. It is just like SDRAM.
• The only difference between the two is that it has a higher
bandwidth, which offers greater speed.
• It’s maximum transfer rate to L2 cache which is approximately
1,064 Mbps.
Secondary
Memory
Secondary Memory
• HDD
- Hard Disk
• SSD
- Solid State Drive
• NVMe
- Non-Volatile Memory Express, or NVMe
HDD
• Introduced in 2003, SATA (or Serial Advanced Technology
Attachment) is the default interface for most desktop and laptop
hard drives.
•
• They are referred to as SATA hard drives, but they are actually rotary
hard drives with spinning platters and a moving needle that writes
data to consecutive sectors on each platter.
• A single drive can range from 250 GB to 16 TB and are available at a
lower cost than any of the other drive types discussed here.
SSD
• SSD stands for Solid State Drive.
• These disks don't have any moving parts.
• Instead, all of the data is stored on non-volatile flash memory.
• That means that there isn't a needle that has to move to read or write data
and that they are significantly faster than SATA drives.
• The downside is that these drives are significantly more expensive and
don't come in as many sizes.
• SSD drives range from about 120 GB to 2 TB, and are about 2-4 times the
price of a SATA hard drive of the same size.
NVMe
• Released in 2013, Non-Volatile Memory Express, or NVMe, is a type
of SSD that's attached to a PCI Express (PCIe) slot on a main board.
• These slots were originally designed for graphics cards, so they are
incredibly fast.
• Speeds on NVMe drives can reach an interface rate of 32 Gb/s with a
throughput of 3.9 GB/s.
• That can be very useful if you are doing something that needs a lot of disk
throughput, like gaming or high-resolution video editing.
• For as fast as it is, there are some drawbacks to NVMes.
• For starters, they are only available on desktop PCs and are very
expensive.
• Also, while they can be used as secondary drives, to use it to its full
potential, you'll want to install your operating system on it.
• Your BIOS may not support booting from NVMe at this time, and in
some cases, it might mean replacing your entire main board.
Choosing a SATA Drive (HHD)
• Need a large amount of storage
• Are on a tight budget
• Need a general purpose hard disk
Choosing an SSD
• You might want to consider an SSD drive if you:
Are upgrading a laptop
• Need fast storage under 2TB
Choosing an NVMe Drive
• Are building a high-end workstation or gaming PC
• Don’t have a budget constraint
• Are building a server that is going to host a storage-intensive
application
Digital Video Disc
Capacity
Designation
Layers
(total)
Sides
Diameter
(cm)
Capacity
(GB)
DVD-1
DVD-2
SS SL
SS DL
1
1
1
2
8
8
1.46
2.65
DVD-3
DS SL
2
2
8
2.92
DVD-4
DVD-5
DS DL
SS SL
2
1
4
1
8
12
5.31
4.70
DVD-9
DVD-10
SS DL
DS SL
1
2
2
2
12
12
8.54
9.40
SS = single-sided, DS = double-sided,
SL = single-layer, DL = dual-layer
Compact Disc (CD)
PCI
Express
PCI Express
PCI Express x1 Slot
Example Cards for PCIe x1 slots:
Port/Hub Expansions
Sound Cards
Network Cards
Capture Cards
PCI Express x4 Slot
Example Cards for PCIe x4 slots:
Port/Hub Expansions
High-Bandwidth Network Cards
NAS Storage
RAID Controller Cards
Capture Cards
M.2 and NVMe Adapters
PCI Express x8 Slot
Example Cards for PCIe x8 slots:
• Higher-Bandwidth Implementations of other Expansion
Cards
• Multi-Slot NVMe Adapters
• Low-End Graphics Cards that are actually made for PCIe x8
slot lengths (something like an AMD RX 560)
PCI Express x16 Slot
Example Cards for PCIe x16 slots:
Graphics Cards, in general
Server-Grade Expansion Cards (Network and Storage most
common)
Thank You