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Hardware, Networking, Mobile
Devices and Troubleshooting
Guide
CompTIA A+ Certification (Exam 220-901)
This document is for evaluation use only. Companies, names, and data used in examples are fictitious unless otherwise noted. The course and materials are designed to familiarize the user with software programs and computer devices. The publisher urges users to review vendor manuals for specific operational questions.
Weighting of Exam Domains
The CompTIA A+ Exam 220-901 is weighted across four domains:
Hardware: 34% Networking: 21% Mobile Devices: 17% Hardware and Network Troubleshooting: 28%
1.0 Hardware
1.1 Motherboard Components
This section covers the importance, purpose, and properties of motherboard components.
Topics include:
Sizes (ATX, Micro-ATX, Mini-ITX, ITX) Expansion slots (PCI, PCI-X, PCIe, Mini PCI) RAM slots CPU sockets Chipsets (Northbridge, Southbridge) CMOS battery Power connections and types Fan connectors Front/Top panel connectors (USB, Audio, Power button, Power light, Drive activity lights, Reset button) Bus speeds
1.2 Connection Interfaces
This section focuses on installing and configuring PC expansion cards.
Types of cards include:
Sound cards Video cards Network cards USB cards Firewire cards Thunderbolt cards Storage cards Modem cards Wireless/cellular cards TV tuner cards Video capture cards Riser cards
1.7 PC Connection Interfaces
This section compares and contrasts various PC connection interfaces, their characteristics, and purpose.
Topics include:
Physical connections USB 1.1 vs. 2.0 vs. 3.0, Connector types: A, B, Mini, Micro Firewire 400 vs.
PC Connector Types and Associated Cables
Connection Interfaces
Common PC connector types include USB, Firewire (IEEE1394), and PS/2. Other connector types are RJ-45, RJ-11, VGA, HDMI, DVI, and Thunderbolt. Wireless connections include Bluetooth, RF, IR, and NFC. Adapters and converters, such as USB A to USB B, USB to Ethernet, and PS/2 to USB, are also used.
Peripheral Devices
Common peripheral devices include input devices like mice, keyboards, biometric devices, game pads, joysticks, motion sensors, touchpads, and smart card readers. Input & output devices include touchscreens and KVMs.
PC Connection Interfaces
Characteristics of PC connection interfaces include analog vs. digital signals, distance limitations, data transfer speeds, quality, and DRM. Firewire 800 is another type of connection interface.
of file fragmentation is eliminated. They are also less susceptible to data loss in the event of power failure. Most drives still feature DRAM-based write cache to improve performance.
SSD Interfaces
An SSD might be installed as the computer's only internal drive or as a system drive for use with an additional hard drive. Consequently, SSDs are now often provided as PCIe adapter cards or as drives that connect to a SATA Express interface.
Storage Technology Comparison
When making a detailed comparison between different types of storage technology, you need to compare performance against different types of data transfer. There are also differences between sequential access and random access. Along with the data throughput (measured in Mbps) and latency / access time, you may need to consider the number of Input / Output Operations per Second (IOPS) that can be achieved by a device for different kinds of data transfer operation.
eMMC Storage
The MultiMedia Card (MMC) format is a legacy type of memory card, similar to SD cards.
Hybrid Drives
In a hybrid drive, the SSD portion functions as a large cache, containing data that is accessed frequently. The magnetic disc is only spun up when non-cached data is accessed. If the SSD is larger, SRT can reserve part of the drive for caching and the remainder of the capacity is then available to the user and can be manipulated via the OS disk and file management tools.
Troubleshooting Hard Drives
Hard drives are most likely to fail due to mechanical problems either in the first few months of operation or after a few years, when they begin to reach the end of their useful life. Sudden loss of power can also damage a disk, especially if it is in the middle of a read/write operation.
Common Symptoms of Disk Failure
A hard drive that is failing will display the following symptoms: Read/write failure, Bluescreen of Death (BSoD), Bad sectors, and unusual noise. 'Disk thrashing' can also be a sign that there is not enough system RAM as data is continually moved between RAM and the pagefile.
Disk Integrity and Diagnostics
You can use the Windows chkdsk utility to verify the integrity of a formatted disk. Most hard drives run a self-diagnostic program called S.M.A.R.T (Self- Monitoring, Analysis, and Reporting Technology) that can alert the operating system if reliability is compromised. In Windows, you can run the following command to perform a S.M.A.R.T check: wmic /node:localhost diskdrive get status. Most hard drive vendors supply utilities for testing drives or there may be a system diagnostics program supplied with the computer system.
Failure to Boot
If the hard drive is not detected at boot (or if a second hard drive is not shown under Windows), first check that it is powering up. If the system is not booting correctly from the hard drive, check that the boot sequence is set correctly in the PC firmware system setup program and that there are no removable disks in floppy or optical drives. If the drives are connected to a motherboard port, check that it has not been disabled by a jumper or via system setup. If a boot hard drive is detected by the firmware hardware check (Power On Self-Test [POST]) but not by Windows, there is probably a problem with the file system.
Boot Errors and Recovery
If typing C: at the command prompt produces the error message Invalid media type, the disk has no valid file system structure on it. If you type C: at the command prompt and this produces the error message Invalid drive specification, the drive may have an invalid partition structure. Damage to the MBR or GPT results in boot errors such as 'OS not found' or 'Invalid drive specification'. If this problem has been caused by a virus, the best way to resolve it is to use the boot disk option in your anti-virus software. If the computer will not boot from a hard disk, you may want to try to recover data from it.
Formatted Capacity
Most disk vendors use decimal measurements to advertise the capacity of disk drives, as this results in a higher value. Windows reports capacity using binary values, but with decimal units.
Low Disk Space and Slow Performance
Slow disk performance is often a bottleneck for modern computer systems. In this case the best solution may be to add more RAM rather than replace the disk or to upgrade the disk to an SSD or hybrid drive. Disk performance can be improved by ensuring that file fragmentation is minimized. Windows warns the user via the notification area when disk space is critically low (below 200 MB).
RAID 10 (RAID 1+0)
RAID 10 combines mirroring and striping. It requires at least four disks, with an even number of disks. In this configuration, one disk in each of the sub-volumes can fail without bringing down the main volume.
Hardware RAID
Hardware RAID is implemented using a plug-in controller card or motherboard support, independent of the operating system. Controllers vary in supported RAID levels. Entry-level controllers support RAID 0 or RAID 1, while mid-level controllers may add RAID 5 and RAID 10. Hardware RAID often supports hot swapping, allowing disk replacement without shutting down the system. The RAID controller synchronizes the new disk with the remaining disks. Modern solutions may use SATA, while SAS is common in server-class machines.
Software RAID
Software RAID is configured within the operating system using standard disks and controllers. Desktop versions of Windows are typically limited to striping. Windows Server versions support mirrored (RAID 1) and striping with parity (RAID 5) arrays. Software RAID can combine internal disks with different interfaces, but does not support USB- or Thunderbolt-connected external drives. Software RAID is cheaper because RAID controller cards can be expensive.
Hot Swappable Drives
Hot swappable drives can be added and removed without powering down the system. They use combined data and power ports on the enclosure, allowing easy access from the front of the case.
Troubleshooting RAID
RAID Failure
RAID protects against hard drive failures through mirroring or parity. Implementation can be via hardware controllers or OS features.
RAID Not Found
If Windows does not detect the RAID array, verify the RAID controller drivers are installed and check the RAID configuration utility.
RAID Stops Working
RAID 1, 5, and 10 are less likely to fail than simple disk systems. RAID 0 has no redundancy, so a single disk failure causes it to stop working. Data backup is crucial in this scenario. Most desktop RAID solutions tolerate only
one disk loss, requiring immediate replacement. Rebuilding the array is done via the RAID configuration utility or Disk Management, which can significantly impact performance.
Disk Handling
Exercise caution when hot swapping disks to avoid removing a healthy disk. Disk failure is usually indicated by a red LED. If too many disks fail or the controller fails, the volume becomes unavailable. In case of too many disk failures, restore from backup or use file recovery solutions. Controller failure may allow data recovery, but file corruption is possible if a write operation was interrupted.
Cooling Systems
Fans
Fans are used to improve the performance of heatsinks on CPUs, GPUs, and hard disks. Power is supplied to fans via headers on the motherboard. Fan connectors and headers are 3-pin or 4-pin.
Liquid-based Cooling Systems
High-end gaming PCs and systems with overclocked components may require liquid-based cooling systems.
Mobile Devices
Mobile Device Types
Mobile devices, such as smartphones and tablets, have gained popularity and replaced traditional computers for many tasks. They use custom operating systems (iOS, Android, or Windows Mobile) and app ecosystems.
Tablets
Tablets are an alternative computing device.
Smart Glasses
Smart glasses use an Optical Head Mounted Display (OHMD) to display information. They connect via Wi-Fi or Bluetooth and may have cellular data adapters.
Battery Considerations
Different battery types necessitate different charging regimes to maximize battery life. Modern Li-ion batteries should not be fully discharged, as this reduces their lifespan.
Disassembling a Laptop
Upgrading components like the CPU and graphics card often requires disassembling the laptop. The general process involves backing up data, preparing the work area with tools and reference materials, and taking anti- static precautions. Disconnect peripheral devices and PCI ExpressCard adapters, and eject discs from drives. Open compartments on the underside and remove Field Replaceable Units (FRUs), including the hard drive, memory, and potentially the optical drive and mini adapter cards. Disconnect the LCD cable and LCD power connector, noting their connections before removing the lid and display assembly. Record the position and orientation of cables and connectors. Remove internal drive cages or heat pipes to access components. Remove the heatsink and fan assembly and drive/adapter card bays to access components on the motherboard, such as the CPU, graphics, and CMOS battery.
Component Replacement
Devices like the screen, keyboard, touchpad, system board, heat pipe, fans, speakers, or DC jack should be replaced using vendor-supplied parts. Upgrading the system board may require updating the chipset driver or notebook system software and allowing Windows to discover the new device using Plug-and-Play.
Graphics
Integrated graphics can improve battery life and cooling. Dedicated graphics are becoming more important as laptops are used as desktop replacements, especially for gaming. Integrated graphics share system memory with the CPU, reducing available system memory. High-end dedicated graphics cards have specific power and cooling requirements, making a modular approach difficult due to space limitations.
Troubleshooting
The same basic troubleshooting approach applies to mobile devices as to desktop PCs, but some issues are specific to laptops. Some laptops require a battery to be present, even when running on AC power. An LED may indicate battery power or charging status. If experiencing problems with AC power, test the outlet with a known good device. Mixed-up AC adapters can cause problems, including the battery not charging, slow performance, and devices not functioning. Try disconnecting drives from media bays or USB and rebooting to see if the problem is fixed. Larger hard drives and external CD/DVD writers typically require their own power supply, even when
connected via USB. A multimeter can be used to check the output of most AC adapters.
