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Computer Memory/Storage
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Measuring Units
BIT: BInary digiT (0 or 1) Word: Natural unit of data used by a particular processor design. The number
of bits in a word (the word size, word width, or word length) is an important characteristic of any specific processor design or computer architecture. Majority of the registers in a processor are usually word sized. (32 bit, 64 bit)
Kilobit: 1000 bits Byte: 8 bits KiloByte (KB): 210 Bytes Kibibyte (KiB): 210 Bytes Binary_prefix:
1 KiB = 210 B, 1MiB = 220 B, 1GiB = 230 B(1 gibibyte) = (210 mebibytes) = (220 kibibytes) = (230 bytes)
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Memory/Storage Categories
Category 1 Main Memory Primary Memory/Storage Internal Memory/Storage
Category 2 Secondary Memory/Storage Auxiliary Memory/Storage External Memory/Storage
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Characteristics
Volatility Volatile Non-volatile
Mutability Read/Write Read Only
Accessibility Random Access Direct Access Sequential Access
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Volatile Memory
Requires power to maintain the stored information Retains the information as long as power supply is on,
but when power supply is off or interrupted the stored memory is lost
RAM 2 main categories
DRAM (Dynamic RAM): RAM, Registers
SRAM (Static RAM): Cache Memory, Registers
Memory Refresh is needed in DRAM and not needed in SRAM
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Non-volatile Memory
Can retain stored information even when not powered
ROM: Read Only Memory Flash Memory F-RAM Most Secondary Storage Devices
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ROM
Read Only Memory Types Optical Storage ROM (CD/DVD/BD ROM) Semiconductor based
PROM: Programmable Read-Only Memory
EPROM: Erasable Programmable Read-Only Memory
EEPROM: Electrically Erasable Programmable Read-Only Memoryo EAROMo Flash Memory
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Read/Write
HDD: Hard Disk Drives Flash Drives Re-Writable Optical Disks SSD: Solid State Drives Also RAM, Cache, Registers
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Read Only
Optical ROM (CD/DVD/BD ROM) Semiconductor ROM
http://en.wikipedia.org/wiki/Write_Once_Read_Many
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Random, Direct, Sequential Access
Random Access Main Memory: RAM, Cache
Direct Access Disks: HDD, Optical Disks
Sequential Access Tapes: Magnetic Tapes (Cassette, VHS)
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Random vs. Sequential Access
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SDRAM - DIMMGenerally in practical world, the term RAM mostly used regarding SDRAM/DIMM
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SDRAM
Synchronous DRAM
SDRAM is DRAM synchronized with the system bus while classic DRAM has an asynchronous interface
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DIMM
Dual In-line Memory Module Series of DRAM integrated circuits
Successor of SIMM (Single IMM)
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Generations of SDRAM
SDR SDRAM: Single Data Rate SDRAM
DDR SDRAM: Double Data Rate SDRAM DDR DDR2 DDR3 DDR4
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DDR SDRAM Comparison
DDR SDRAM Standard
Bus clock (MHz)
Transfer Rate (MT/s)
Voltage (V)
DIMM pins
DDR(1) 100–200 200–400 2.5/2.6 184
DDR2 200–533 400–1066 1.8 240
DDR3 400–1066 800–2133 1.5 240
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Key Values of a DIMM
Generation (DDR2, DDR3)
Frequency/Data Rate (1333, 1600)
Capacity (2048 MB, 4 GB)
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Determine Generation/Data Rate
Some vendors do not print DRAM generation/frequency in labels directly
But most of them label module names which contains generation and bandwidth info
PCX-# The Generation is X and the memory bandwidth is # Memory Frequency and Data Rate can be determined using memory
bandwidth
Examples PC-3200 : DDR, 400 (3200/8=400) PC2-6400: DDR2, 800 (6400/8=800) PC3-12800: DDR3, 1600 (12800/8=1600)
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DIMM Vendors
Kingston G.Skill Toshiba Samsung Hynix Corsair
+ many more(Not in Particular Order :)
HDDHard Disk Drives
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HDD: Hard Disk Drives
Direct Access Storage Used for storing and retrieving digital information using rapidly rotating
discs (platters) coated with magnetic material Records data by magnetizing a thin film of ferromagnetic material on a
disk Consists of a spindle that holds flat circular disks, also called platters,
which hold the recorded data Platters in most consumer HDDs spin in the range of 5,400 rpm to
7,200 rpm Information is written to and read from a platter as it rotates past
devices called read-and-write heads that operate very close over the magnetic surface
Modern drives there is one head for each magnetic platter surface on the spindle
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HDD Capacity
Capacity measured by GB, TB Vendors and Operating System uses 2 different methods
to measure HDD capacity Vendors use 1000 metric (SI) method (1KB=1000B) as a
marketing trick and OS uses 1024 method (1KB=1024B) which is similar to binary prefix method
Therefore labeled size is different from the size we see from the size shown by the OS
Examples: 1TB : 931.32 GB 500GB : 465.66 GB
(Actual Usable Size may also differ…)
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HDD Performance
RPM: Rotations Per Second 5400, 7200, 10000… etc.
Latency: The delay for the rotation of the disk to bring the required disk sector
Seek Time: The time for the actuator arm to reach the desired disk track
Access Time = Seek Time + Latency
Data Transfer Rate
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HDD Interface
http://en.wikipedia.org/wiki/Hard_disk_drive_interface
(P)ATA: Parallel ATA
SATA: Serial ATA
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SATA vs. PATA
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External HDD
External/Portable HDDs typically connect through USB or eSATA ports
Most External HDDs now use USB 3.0 interface External HDDs are Slower, compared to Internal
HDDs Certain Portable HDDs
have extra features such as special Encryption methods, Security Options, Shock Protection, etc…
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HDD Related Terms
ECC: Error Correcting Code http://en.wikipedia.org/wiki/Forward_error_correction
S.M.A.R.T: Self-Monitoring, Analysis and Reporting Technology http://en.wikipedia.org/wiki/S.M.A.R.T
Disk Buffer/Cache: Embedded memory acting as a buffer between the computer and the physical hard disk platter. Usually 8 to 128 MiB
RAID: Redundant Array of Independent Disks http://en.wikipedia.org/wiki/RAID
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HDD Vendors
Samsung Seagate Western Digital Hitachi Quantum Toshiba
+ many more[Not in Particular Order :]
Optical StorageCD, DVD, BD
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Optical Storage Devices
Optical storage is a storage method in which data is written and read with a optical beam (laser)
ODD: Optical Disk Drive Typically used for archival or backup purposes Slower than HDDs Less vulnerable to environmental conditions Data stream is placed in a spiral path. The data begins at the
innermost track and works its way out toward the edge of the disc Data is read by a laser beam always Data is also written/burned by laser beams,
but in industrial mass produced discs, the data is placed on the disc by a stamping machine
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Optical Disc Generations
First-generation CD
Second-generation DVD
Third-generation BD
Fourth-generation HVD
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CD: Compact Disc
Developed by: Philips, Sony Read mechanism: 780 nm wavelength (
infrared and red edge) semiconductor laser(Speed 1200 Kib/s = 1×, Generally 52×)
CD-R (Compact Disc-Recordable) CD-RW (Compact Disc-ReWritable) Capacity: ~ 700 MiB
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DVD
Developed by: Philips, Sony, Toshiba, and Panasonic in 1995 Read mechanism: 650 nm laser,
(Speed 10.5 Mbit/s = 1×, Generally 16×) Recordable DVDs: DVD-R and DVD+R Re-Writable DVDs: DVD-RW, DVD+RW, and DVD-RAM Capacity: ~ 4.7 GiB DVD was an acronym (initialism) for the unofficial Digital
Video Disk. Later the Backronym Digital Versatile Disc was introduced to express that DVD goes beyond video (Data, Software, Audio). However it was not universally accepted and a 1999 report decreed that DVD was "simply three letters" and stood for "nothing".
Today, usage varies and there is no universal agreement. Digital Versatile Disc has gained wide acceptance
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BD: Blu-ray Disc
Designed to supersede DVD BD is 120 mm in diameter and 1.2 mm thick,
the same size as DVD and CD Developed by: Blu-ray Disc Association Read mechanism: 405 nm diode laser.
(Speed 36 Mbit/s = 1×, Generally 2×) Capacity: ~ 25 GB
BD-ROM (read-only) - for pre-recorded content BD-R (recordable) - for PC data storage BD-RE (rewritable) - for HDTV recording BD-RW (rewritable) - for PC data storage Blu-ray 3D, BD-XL, Printable Blu-ray
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BD: Blu-ray Disc
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Optical Staroge Read-Write
http://www.howstuffworks.com/blu-ray2.htmhttp://www.cd-info.com/blu-ray/
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HVD: Holographic Versatile Disc
The Holographic Versatile Disc (HVD) is an optical disc technology developed between April 2004 and mid-2008
Can store up to several terabytes of data on an optical disc 10 cm or 12 cm in diameter
Media type: Ultra-high density optical disc Capacity: ~ 6 TB
Flash Drives
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Flash Drive Types
Generic Solid-State Drives USB Flash Drives and Memory Cards
Specific● CompactFlash (CF)● Multimedia Card (MMC)● Memory Stick (MS)● Secure Digital (SD, SDHC, SDXC)
SSDSolid-State Drives
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SSD: Solid State Drives
A data storage device using integrated circuit assemblies as memory to store data persistently
Unlike HDDs, SSDs have no moving mechanical components
SSHD Hybrid drives or solid state hybrid drives (SSHD)
combine the features of SSDs and HDDs in the same unit, containing a large hard disk drive and an SSD cache to improve performance of frequently accessed data
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SSD vs HDD
SSD (Compared to HDD)… High Cost High Speed Low Access Time Low (No) Noise Less susceptible to physical shock and magnetic fields Less Power Consumption and Less Heat Generation Smaller in Physical Size Smaller in Capacity
https://duckduckgo.com/?q=SSD+vs+HDDhttps://www.google.com/search?q=SSD+vs+HDD
USB Flash Drive
Pen DriveJump DriveThumb Drive
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USB Flash Drives
AKA: Pen Drive, Jump Drive, Thumb Drive
Uses a Flash Memory Chip Has a USB Connector,
Mostly USB 2.0 or 3.0 Usually very small in physical size and
come in different shapes
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USB Flash Drives
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Memory Cards
Used by Mobile Phones, Digital Cameras, Music players , etc.
Memory Cards use a Flash Memory Chip
Memory Card Types CompactFlash (CF) Multimedia Card (MMC) Memory Stick (MS) Secure Digital (SD, SDHC, SDXC)
(More)
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SD Card: Secure Digital Card
Most mobile devices uses SD cards now
SD specification (Capacity) SD – SDSC (SD Standard Capacity) SDHC (SD High Capacity): Up to 32 GB SDXC (SD eXtended Capacity): Up to 2 TB
Physical Size Standard: SD
Mini: miniSD
Micro: microSD
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SD, miniSD, microSD Comparison
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Card Readers
Memory Card readers are used to read/write singe or multiple types of Cards (CF, MMC, MS, SD)
USB and PCI Card Readers are available Most Notebook Computers and some
desktop PCs Contain Internal Card Readers
USB microSD card readers much similar to a Pen Drive
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Card Readers
Online Storage
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Online Storage http://en.wikipedia.org/wiki/Online_file_storage http://en.wikipedia.org/wiki/Cloud_storage
Google Drive: https://drive.google.com
SkyDrive https://skydrive.live.com
DropBox https://www.dropbox.com
SugarSync https://www.sugarsync.com
Amazon Cloud Drive http://www.amazon.com/gp/feature.html?ie=UTF8&docId=1000828861
Thank You! :)
Ayubowan!
