Test 1001 of the CompTIA A+ Core Series contains questions about five topics and one of them is Hardware. These questions will occupy about 27% of the 1001 test and about two-thirds of them will begin with the description of a scenario you could encounter in real life. Then, you’ll be asked to choose a solution. We’ve noted in which topics this might happen with the designation (of scenario) below.
You must be able to describe different cable types and their characteristics and uses.
Network cables connect devices to the network. The most common types are Ethernet, fiber, and coaxial cable.
Ethernet cables use twisted pairs of copper wire. It may be shielded or unshielded. Each category of cable has specific physical characteristics and a maximum data rate. Ethernet cables have a maximum length of 100 meters.
Cat 5—Category 5 cable supports data rates up to 100 Mbps.
Cat 5e—Category 5e cable supports data rates up to 1 Gbps.
Cat 6—Category 6 cable supports data rates up to 10 Gbps up to 55 meters and 1 Gbps up to 100 meters.
Plenum—Plenum cable is used in the plenum space of a building. Any space that handles air circulation in an HVAC system is plenum space, typically above a drop ceiling or below a raised floor. Plenum cable uses low-smoke and low-flame materials for fire prevention.
Shielded twisted pair—STP Ethernet cable uses two or four pairs of copper wire. It uses a foil or braided shield to reduce electromagnetic interference. Depending on the type of cable, each twisted pair may be shielded or a single shield covers all twisted pairs.
Unshielded twisted pair—UTP Ethernet cable uses two or four pairs of copper wire. The twist in the wires reduces electromagnetic interference.
568A/B—Ethernet cables are terminated with RJ-45 connectors. The pin-out (which wire connects to which pin) of those connectors is defined in the EIA/TIA 568A & 568B Standards. The difference between 568A and 568B is that the transmit and receive pairs are reversed. This allows for two types of cables, straight-through and crossover.
Straight-through is used to connect a device to the network via a switch or hub. It uses the same pin-out on both ends, whether 568A or 568B. A crossover cable is used to connect one device directly to another, such as two computers, without a switch or hub between them. Crossover cables use 568A on one end and 568B on the other.
Fiber optic cable uses light pulses to transmit data through a glass or plastic core. The cable consists of four layers. The core is surrounded by a cladding that refracts light back into the core. The other two layers are the outer sheath, the part you see, and a strength member or buffer to protect the fiber.
Fiber is not subject to electromagnetic interference, since it uses light to transmit data. Transmission distances are longer and data rates are higher on fiber than they are on copper cable. There are two basic types of fiber, single-mode and multimode. Single-mode fiber carries only one light path, typically sourced by a laser. Multimode carries multiple light paths and is sourced by an LED. Single-mode has a much longer transmission distance than multimode.
Coaxial cable is used primarily for cable Internet service and audio/video applications such as cable TV. It has a single copper conductor core surrounded by a dielectric insulator and one or more layers of shielding. The shielding reduces electromagnetic interference. The two most common types of coaxial cable are RG-6 for data and RG-59 for audio/video.
Speed and Transmission Limitations
Each type of network has speed and distance limitations.
Category 5 cable supports data rates up to 100 Mbps.
Category 5e cable supports data rates up to 1 Gbps.
Category 6 cable supports data rates up to 10 Gbps up to 55 meters and 1 Gbps up to 100 meters.
The most commonly used fiber is multimode and supports data rates up to 100 Mbps up to 2000 meters, 1 Gbps up to 550 meters, and 10 Gbps up to 300 meters.
Video cables connect a specific type of video port on a computer to a display. Each has its own connector type and cable pin-out.
VGA— VGA cables connect older analog Video Graphics Adapters to a display. It uses a 15-pin connector arranged in three rows of five pins.
HDMI—HDMI cables connect a High Definition Multimedia Interface to a display. It uses a 19-pin connector arranged in two rows. There are different types of HDMI cables. The most commonly used is type A but is usually just referred to as an HDMI cable with no type designation.
Mini-HDMI—HDMI type C is usually referred to as mini-HDMI. It uses a 19-pin connector arranged in two rows, like the HDMI type A cable, but it is smaller and the pin-out is different.
DisplayPort—DisplayPort cables connect a DisplayPort interface to a display. It uses a 20-pin connector arranged in two rows of ten pins.
DVI (DVI-D/DVI-I)—DVI cables connect a Digital Visual Interface interface to a display. DVI-D (-D for digital) supports only digital signals. DVI-I (-I for integrated) supports digital and analog signals. There are single-link and dual-link DVI cables. Single-link DVI supports 3.7 Gbps HDTV at 60 frames per second. Dual-link DVI supports 7.4 Gbps HDTV at 85 frames per second.
Connecting devices directly together without a network connection can be done with these cables.
Lightning—Lightning cables are proprietary to Apple?. They are used to connect Apple? devices to USB ports. The cable has eight wires and is terminated with a USB connector on one end and a Lightning connector on the other. It can carry both data and power to charge the device. The Lightning connector is reversible, so it can be plugged into the device without regard to which side is up.
Thunderbolt—Thunderbolt is another Apple?-proprietary cable. It comes as either copper or optical cable. The maximum length is 3 meters for copper and 60 meters for optical cable. The connectors are based on the Mini DisplayPort standard, except Thunderbolt version 3 uses a USB-C connector on the peripheral end. It provides both data and power to peripheral devices, most commonly storage and display devices. There are three versions of Thunderbolt. Total throughput for Thunderbolt 1 and 2 is 20 Gbps and Thunderbolt 3 is 40 Gbps.
USB—Universal Serial Bus cables connect to a wide variety of peripheral devices. USB 1.1 was the first version in common use. It uses a type-A connector on the PC side and a type-B connector on the peripheral side. There are also mini and micro connectors for smaller devices such as cell phones and cameras. It supports two speeds. Low speed supports data transfer rate of 1.5 Mbps at lengths up to 3 meters. Full speed supports data transfer rates of 12 Mbps at lengths up to 5 meters. It provides power, as well.
USB-C—USB-C is a connector type that is used on USB 3.0 and newer cables.
USB 2.0—USB 2.0 maintains the characteristics of USB 1.1 and adds a high-speed data transfer rate of 480 Mbps at lengths up to 5 meters.
USB 3.0—USB 3.0 maintains the characteristics of USB 2.0 and adds SuperSpeed data transfer rate of 5 Gbps at lengths up to 3 meters. The connectors are a bit different, adding pins to some connectors to support the higher transfer rate, as well as adding the type-C connector.
Other Cable Types
Connections to serial ports and hard drives are done with specific cables discussed in this section. In some instances, adapters can be used to connect to devices.
Peripheral cables are used to connect a PC to other devices.
Serial—While there are many types of serial cables, the term “serial cable” usually refers to a specific type of cable that confirms to the RS-232 specification. Serial cables are most often used to connect a laptop to the console or management port of a network device, such as a switch, router, or firewall.
Hard Drive Cables
Hard drive cables connect a hard drive to a motherboard or controller card. The same cables may also be used to connect optical drives and older floppy drives.
SATA—The Serial Advanced Technology Attachment (SATA) cable is the most commonly used hard drive cable. There are different SATA revisions. They all allow a maximum cable length of one meter. SATA revisions 1.0, 2.0, 3.0, and 3.2 support speeds of 1.5 Gbps, 3 Gbps, 6 Gbps, and 16 Gbps, respectively.
IDE—Integrated Drive Electronics is an older interface. The IDE cable is a 40-wire (34-wire for floppy drives) ribbon cable that is connected from the motherboard on one end to one or two drives on the other end.
SCSI—Small Computer System Interface was designed to support a wide variety of device types, so there are different types of SCSI cables. They may be ribbon cables or standard round cables of 50, 68, or 80 wires. Up to 16 devices, including the motherboard or SCSI controller card, may be connected to one SCSI cable or daisy-chained together.
Adapters may be used to connect a device to a port that is different from the connector on the device. They are most often used to connect to a display or a network.
DVI to HDMI—This connects a DVI port to an HDMI display. DVI does not carry audio, so a separate connection is needed to carry audio to the display.
USB to Ethernet—This connects a USB port on a computer to an Ethernet port on a network device.
DVI to VGA—This connects a DVI port to a VGA display.
You must be able to identify different connectors that are commonly used to connect to computers, peripherals, and network devices.
RJ-11—RJ-11 is the plain old telephone system connector. It is a single-row 6-pin rectangular connector to connect to a phone system or modem.
RJ-45—Often referred to as an Ethernet connector, this single-row 8-pin rectangular connector is used for Ethernet connections.
RS-232—RS-232 is actually a specification for serial communications that uses either a DB-9 or DB-25 connector. It has a trapezoid shape. The DB-9 is a 9-pin connector arranged in two rows of four and five pins. The DB-25 is a 25-pin connector arranged in two rows of 12 and 13 pins. RS-232 is most commonly used to connect to network devices’ console or management ports.
BNC—BNC connectors are used to terminate DS3 coaxial cables, used for wide area network connections. An older type of Ethernet network known as 10Base2 or Thinnet also used coaxial cable terminated with BNC connectors. It is a cylindrical connector with a twist-lock end to make a secure connection.
RG-59—Cable TV coaxial cables are terminated with RG-59 connectors, cylindrical connectors with a threaded end to make a secure connection.
RG-6—Cable Internet coaxial cables are terminated with RG-6 connectors, cylindrical connectors with a threaded end to make a secure connection.
USB—The Type-A USB connector is a rectangular 4-pin connector that connects to a computer. The Type-B USB connector is a 4-pin connector that connects to a peripheral device. It is basically square, but two corners are cut at an angle.
Micro-USB—The micro-USB connector is a 5-pin connector that connects to a peripheral device. It is basically rectangular, but two corners are cut at an angle.
Mini-USB—The mini-USB connector is a 5-pin connector that connects to a peripheral device. It is basically rectangular, but two corners are cut at an angle on one side, and two tabs are on the other side.
USB-C—The USB-C connector is an oval 24-pin connector that connects to either a computer or peripheral device. It is reversible, meaning that it may be inserted with either side up. It has two rows of 12 pins. Each row carries the same set of signals.
DB-9—The DB-9 is a trapezoid-shaped 9-pin connector arranged in two rows of four and five pins. It is used for serial connections to network devices’ console or management ports.
Lightning—The Lightning connector is a rectangular 8-pin connector that connects to either a peripheral device. It is reversible, meaning that it may be inserted with either side up. It has a single row of 8 pins that are exposed on both sides of the connector.
SCSI—There are different types of SCSI connectors. The most common are rectangular or trapezoidal with 50 or 68 pins arranged in two rows.
eSATA—The external SATA (eSATA) connector is a 7-pin connector that connects to an external SATA drive. It has basically a rectangular shape with tabs on the ends.
Molex—The most common Molex connector is a single-row 4-pin connector used to provide power to disk drives. It has a basically rectangular shape with two corners cut at an angle.
You need to understand the different types of random-access memory and how to install them.
Small Outline Dual Inline Memory Modules are commonly found in laptops and come in 100-, 144-, 200-, 204-, and 260-pin configurations. SODIMM defines the physical form factor of the module.
Double data rate (DDR) refers to the speed of data transfer. DDR2 and has less power consumption and is faster than the original DDR RAM. It comes in 240-pin DIMM and 200-pin SODIMM.
DDR3 is faster than DDR2 and has 30% less power consumption. It comes in 240-pin DIMM and 204-pin SODIMM.
DDR4 is faster than DDR3 and has less power consumption. It comes in 288-pin DIMM and 260-pin SODIMM.
A single channel RAM architecture moves data on a single data bus, typically 64-bits at a time.
A dual channel RAM architecture moves data on two data buses, typically 128-bits at a time.
A triple channel RAM architecture moves data on three data buses, typically 192-bits at a time.
Error Checking and Correcting (ECC) memory 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.
Parity vs. Non-Parity
Memory with parity has logic built in to detect single-bit memory errors. For each byte (eight bits) of memory, a parity bit is set that will allow the logic to detect an error in a single bit of each byte. The logic may or may not detect an error in any byte with more than one bad bit. While parity allows for the detection of memory errors, it does not correct those errors. Additional logic, such as ECC, would be needed for error correction.