220-1201 Hardware Study Guide for the CompTIA A+ Core Series Exam

Random Access Memory (RAM)

RAM is the memory bank for data currently in use by a computer or device. RAM is temporary, and there are numerous types. You must be able to identify, compare, and contrast different RAM types. These questions will be scenario-based.

Form Factors

A form factor is the physical size and shape of a hardware component. The form factor of a component, such as RAM, dictates compatibility with other components, such as the motherboard. RAM has two common form factors, DIMM and SODIMM.

Dual In-Line Memory Module (DIMM)

DIMMs are the most common RAM form factors and are primarily used in desktop computers. DIMM modules can be either standard-sized, used for full-size computers, or low-profile, used in smaller computers with limited space in the housing.

Small Outline Dual In-Line Memory Module (SODIMM)

SODIMMs are commonly found in laptops where space is at a premium and commonly have either 200-pin (DDR1/2), 204-pin (DDR3), or 260-pin (DDR4) configurations.

Double Data Rate (DDR) Iterations

Double data rate (DDR), as the name implies, doubles the transfer rate of memory. DDR2 further increases the speed by two. DDR and DDR2 are legacy technologies and are no longer used in modern devices. DDR3 is faster than DDR2 and has 30% less power consumption. It comes in 240-pin DIMM and 204-pin SODIMM form factors. DDR4 is faster than DDR3 and requires less power consumption. It comes in 288-pin DIMM and 260-pin SODIMM form factors. DDR5 doubles the speed of DDR4 to 6.4 Gbps, with improved power efficiency at 1.1 volts, and is available in up to 128 GB modules.

Error-Correcting Code (ECC) vs. Non-ECC RAM

ECC RAM is commonly used in servers or systems where data integrity is critical and has logic built in to detect and correct single-bit memory errors. For each byte (eight bits) of memory, a parity bit is set that will allow the logic to detect and correct an error in a single bit of each byte. The logic would not correct an error in any byte with more than one bad bit. Non-ECC RAM is commonly used in standard consumer computers and does not have ECC capabilities, which allows it to have increased speed.

Channel Configurations

Single-channel memory transfers data in chunks the same size as the system bus’s bandwidth. Dual-channel memory describes when the memory controller coordinates two memory banks to work in conjunction with one another as a synchronized set when communicating with the CPU, doubling the size of the data transfer. Triple-channel memory coordinates three memory modules for communication with the CPU, and quad-channel memory coordinates four memory modules.

Storage

Storage devices are physical components used to store data and files that a computer system needs to operate. You must be able to identify, compare, and contrast different storage devices. Questions about these devices will be scenario-based.

Hard Drives

A hard drive is a non-volatile storage device designed for quick access. It is also known as a hard disk drive (HDD) or a conventional drive and uses a magnetic spinning internal platter to store memory.

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Spindle Speeds

The speed at which an HDD operates is measured by the number of revolutions per minute (rpm) that the platter of an HDD spins. Higher speeds use more energy and increase heat production. There are four HDD speeds: 5,400 rpm, 7,200 rpm, 10,000 rpm, and 15,000 rpm.

Form Factors

The form factor refers to the physical size of the hard drive. There are two hard drive form factors, both of which contain the same connectors.

2.5-Inch

The 2.5” hard drives are typically used in laptops. They can be mounted in a 3.5” form factor slot with the use of a converter kit.

3.5-Inch

The 3.5” hard drives are typically used in desktop computers.

Solid-State Drives

A solid-state drive (SSD) is flash memory technology that contains no moving parts. Flash memory is a form of nonvolatile read/write memory. Nonvolatile memory retains data when power is removed. Flash erases data in blocks rather than at the byte level. An SSD uses a series of NAND chips to store memory. SSDs can be made in smaller form factors than HDDs and are capable of much higher speeds.

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Communications Interfaces

Communication interfaces are the method through which an SSD communicates with the motherboard and other components. These are the main types of interfaces:

• Non-Volatile Memory Express (NVMe) is an open-source standard used to optimize data transfer and can support speeds up to 3.5 GBps.

• The Serial Advanced Technology Attachment (Serial AT Attachment or SATA) interface is the slowest of the SSD interfaces.

• Peripheral Component Interconnect Express (PCIe) offers faster speeds than SATA but slower than NVMe.

• The Serial Attached Small Computer System Interface (SCSI), or simply SAS, is used for high-performance computing devices such as enterprise-level storage devices.

Form Factors

These form factors of SSDs define their shape and size.

M.2

M.2 is a form factor for SSDs that is 22 millimeters wide and can vary in length, with the most common lengths being 80 millimeters and 60 millimeters. It is referred to as “gumstick memory” because its size is similar to a stick of gum. M.2 drives plug into an M.2 slot on a motherboard.

Mini-Serial Advanced Technology Attachment (mSATA)

mSATA is a form factor that has a 30-millimeter wide, 52-pin connector and uses the SATA interface for communication. mSATAs can be either 30 millimeters by 50.95 millimeters or 30 millimeters by 26.8 millimeters.

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Drive Configurations

Storage devices can be configured for high availability so that if one disk in an array of disks fails, data is not lost. The most common configuration is known as a redundant array of independent (or inexpensive) disks.

Redundant Array of Independent Disks (RAID) 0, 1, 5, 6, 10

There are different RAID configurations, known as RAID 0, 1, 5, 6, and 10, that provide varying levels of data protection. These configurations offer striping, a method of storing part of the data on each drive in an array, and/or mirroring, which involves keeping a full copy of a disk on another disk. This is how each configuration works:

• RAID 0—This configuration offers striping of data only, with no redundancy but good performance.

• RAID 1—This configuration offers mirroring of data only, which requires more storage space to store full copies of data.

• RAID 5—This configuration offers striping with parity, requires a minimum of three drives, and has the ability to calculate missing data and rebuild.

• RAID 6—This configuration offers stripping with double parity and requires a minimum of four drives.

• RAID 10—This configuration offers striping and mirroring for full redundancy, with a minimum of four drives.

Removable Storage

Removable storage devices are not contained internally but externally and can be relocated.

Flash Drives

Flash drives are removable storage devices that are capable of containing a large quantity of information in a non-volatile, small, and portable form. Flash memory devices include Secure Digital (SD) cards, USB flash drives, and optical cards.

Memory Cards

A memory card is a memory device that can store data in a non-volatile state. Common memory card form factors include CompactFlash (CF), SD, and microSD.

Optical Drives

Optical cards are storage devices that store data through the use of lasers on spinning discs. Examples of optical cards include compact discs (CDs), digital video discs (DVDs), and Blu-ray discs (BDs).