← CompTIA A+ Hardware & Components

CompTIA A+ Certification Study Guide

Key concepts, definitions, and exam tips organized by topic.

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CompTIA A+ Hardware & Components Study Guide


Overview

This study guide covers the essential hardware and component knowledge required for the CompTIA A+ certification exam. Topics include CPU architecture, motherboard chipsets, memory, storage interfaces, power delivery, expansion cards, and thermal management. Mastery of these concepts is critical for both the Core 1 (220-1101) exam and real-world PC building and troubleshooting scenarios.


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CPU & Motherboard


Key Concepts


The CPU (Central Processing Unit) is the primary processing component of a computer system, and its compatibility is determined largely by the socket type on the motherboard. Modern CPUs integrate functions that were historically handled by separate chipset components.


Intel Socket Types:

  • • LGA1700 — Intel 12th Gen (Alder Lake) and 13th Gen (Raptor Lake)
  • • LGA1200 — Intel 10th and 11th Gen
  • • LGA1151 — Intel 6th through 9th Gen
  • • Sockets are not backward compatible between generations

    • AMD Socket Types:

  • • AM5 — Ryzen 7000 series and newer
  • • AM4 — Ryzen 1000 through 5000 series

    • Chipset Architecture


    | Era | Architecture | Description |

    |---|---|---|

    | Traditional | Northbridge + Southbridge | Northbridge managed CPU ↔ RAM ↔ GPU; Southbridge handled I/O |

    | Modern | Single PCH | Northbridge functions integrated into the CPU die itself |


    The Northbridge historically handled high-speed communication between the CPU, RAM, and GPU via the front-side bus (FSB). In modern systems, the memory controller and PCIe controller live directly on the CPU, eliminating the Northbridge entirely.


    Motherboard Form Factors


    | Form Factor | Dimensions | Use Case |

    |---|---|---|

    | ATX | 9.6 × 12 in | Full desktop builds; most expansion slots |

    | Micro-ATX | 9.6 × 9.6 in | Compact builds; fewer slots |

    | Mini-ITX | 6.7 × 6.7 in | Small form factor; very limited expansion |

    | E-ATX | 12 × 13 in | Workstation/enthusiast builds |


    > Note: The 9.6 × 9.6 in dimension belongs to Micro-ATX, not ATX. Standard ATX is 9.6 × 12 in.


    BIOS/UEFI


    POST (Power-On Self-Test) is the first process that runs when a computer powers on. It verifies:

  • • CPU presence and function
  • • RAM detection
  • • Storage device presence
  • • Video output capability
  • • Other essential hardware

    • UEFI vs. Legacy BIOS:


    | Feature | Legacy BIOS | UEFI |

    |---|---|---|

    | Partition style | MBR | GPT |

    | Max drive size | 2 TB | 9.4 ZB theoretical |

    | Interface | Text-only | Graphical |

    | Boot speed | Slower | Faster |

    | Secure Boot | No | Yes |

    | Bit mode | 16-bit | 32/64-bit |


    CMOS Battery

  • • Type: CR2032 lithium coin cell
  • • Function: Maintains BIOS settings and real-time clock when power is removed
  • • Symptom of failure: System loses time/date, BIOS reverts to defaults, "CMOS checksum error"

    • CPU Multi-Threading


    | Technology | Vendor | Description |

    |---|---|---|

    | Hyper-Threading (HT) | Intel | 1 physical core = 2 logical processors |

    | Simultaneous Multi-Threading (SMT) | AMD | Same concept, AMD's implementation |


    Thermal Paste

  • • Fills microscopic air gaps between the CPU Integrated Heat Spreader (IHS) and the cooler base
  • • Improves thermal conductivity
  • • Should be replaced when reseating a cooler
  • • Excess paste can cause thermal issues or short circuits if it spills onto PCB contacts

    • Key Terms

  • • LGA (Land Grid Array) — Pins are on the motherboard socket, not the CPU
  • • PGA (Pin Grid Array) — Pins are on the CPU (used by AMD AM4)
  • • IHS (Integrated Heat Spreader) — Metal lid on top of the CPU die
  • • TDP (Thermal Design Power) — Maximum heat the cooling system must dissipate
  • • FSB (Front-Side Bus) — Legacy communication path between CPU and Northbridge
  • • PCH (Platform Controller Hub) — Modern single-chip replacement for Northbridge/Southbridge

    • Watch Out For

    > ⚠️ Micro-ATX vs. ATX dimensions are commonly confused on exams. ATX = 9.6 × 12 in; Micro-ATX = 9.6 × 9.6 in.

    >

    > ⚠️ LGA sockets have pins on the motherboard — be careful not to bend them during installation.

    >

    > ⚠️ Hyper-Threading does not double performance — it improves multi-threaded efficiency but both logical cores share one physical core's resources.


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    RAM (Random Access Memory)


    Key Concepts


    RAM is volatile memory used for active processes and data. The type, speed, and configuration of RAM significantly impact system performance.


    DDR Generations Comparison


    | Specification | DDR4 | DDR5 |

    |---|---|---|

    | Base speed | 2133 MT/s | 4800 MT/s |

    | Max speed (common) | 3200 MT/s | 6400+ MT/s |

    | Voltage | 1.2V | 1.1V |

    | On-die ECC | No | Yes |

    | IMC location | CPU | CPU |

    | Compatibility | Not cross-compatible | Not cross-compatible |


    > DDR4 and DDR5 are physically incompatible — different notch positions prevent incorrect installation.


    Memory Channels


  • • Single-channel: One stick using one 64-bit bus
  • • Dual-channel: Two sticks using two 64-bit buses simultaneously = 128-bit effective bus width
  • • Quad-channel: Four sticks (common in workstation/HEDT platforms)

    • To enable dual-channel:

  • • Install matching RAM sticks
  • • Use the correct paired slots (typically slots 2 & 4, or color-coded pairs)
  • • Consult the motherboard manual for exact slot pairing

    • ECC RAM

  • • Error-Correcting Code RAM detects and corrects single-bit memory errors
  • • Detects (but cannot correct) double-bit errors
  • • Requires compatible CPU and motherboard (typically server/workstation platforms)
  • • Slightly slower than non-ECC due to error-checking overhead
  • • Critical environments: Servers, financial systems, medical equipment, scientific computing

    • XMP / EXPO Profiles


    | Profile | Vendor | Function |

    |---|---|---|

    | XMP (Extreme Memory Profile) | Intel | Auto-applies advertised RAM overclock speeds |

    | EXPO (Extended Profiles for Overclocking) | AMD | AMD's equivalent for AM5 platform |


    Without enabling XMP/EXPO in BIOS, DDR4/DDR5 defaults to slower JEDEC standard speeds.


    Troubleshooting RAM


    System only detects partial RAM:

  • • Wrong slots populated (not using paired slots for dual-channel)
  • • One or more sticks are faulty or not fully seated
  • • Motherboard has a maximum RAM capacity limit
  • • CPU or chipset limits addressable RAM
  • • RAM is incompatible with the platform (e.g., DDR5 in a DDR4 board)

    • Key Terms

  • • DIMM (Dual Inline Memory Module) — Standard desktop RAM form factor
  • • SO-DIMM (Small Outline DIMM) — Laptop and compact system RAM form factor
  • • MT/s (Megatransfers per second) — Correct speed rating unit (often mislabeled as MHz)
  • • Latency (CL) — Number of clock cycles to access data; lower is faster
  • • JEDEC — Standards body that defines base RAM speeds

    • Watch Out For

    > ⚠️ RAM must be installed in the correct paired slots for dual-channel — not just any two slots.

    >

    > ⚠️ XMP must be manually enabled in BIOS — RAM will not run at advertised speeds by default.

    >

    > ⚠️ ECC RAM is not universally supported — the CPU and motherboard must explicitly support it.


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    Storage Devices


    Key Concepts


    Storage comes in multiple interfaces and form factors with dramatically different performance characteristics. Understanding the differences between SATA, NVMe, and M.2 is essential.


    Interface Speed Comparison


    | Interface | Protocol | Max Speed | Use Case |

    |---|---|---|---|

    | SATA III | AHCI | ~600 MB/s | HDDs, SATA SSDs |

    | M.2 SATA | AHCI | ~550 MB/s | Compact SATA SSDs |

    | M.2 NVMe (PCIe 3.0) | NVMe | ~3,500 MB/s | Modern SSDs |

    | M.2 NVMe (PCIe 4.0) | NVMe | ~7,000 MB/s | High-performance SSDs |

    | M.2 NVMe (PCIe 5.0) | NVMe | ~14,000 MB/s | Enthusiast SSDs |


    HDD vs. SSD Comparison


    | Feature | HDD | SSD |

    |---|---|---|

    | Storage medium | Magnetic platters | NAND flash memory |

    | Moving parts | Yes (platters + head) | No |

    | Speed | 80–160 MB/s | 500–7000+ MB/s |

    | Shock resistance | Low | High |

    | Noise | Audible | Silent |

    | Lifespan metric | MTBF | TBW (Terabytes Written) |

    | Cost per GB | Lower | Higher |


    HDD Spindle Speeds:

  • • 5400 RPM — Laptops, external drives, low-power NAS
  • • 7200 RPM — Desktop HDDs, better performance
  • • 10,000–15,000 RPM — Enterprise SCSI/SAS drives

    • M.2 Form Factor Details


    M.2 is a physical form factor, not a protocol. An M.2 slot can support either SATA or NVMe depending on the slot's wiring.


    M.2 Key Types:


    | Key Type | Supported Protocols | Common Use |

    |---|---|---|

    | B-key | SATA, PCIe x2 | Older SATA SSDs |

    | M-key | SATA, PCIe x4 (NVMe) | Most modern SSDs |

    | B+M key | SATA or PCIe x2 | Universal compatibility |


    M.2 Physical Sizes (Length):

  • • 2242, 2260, 2280 (most common), 22110

    • > Not all M.2 slots support both SATA and NVMe — always check the motherboard manual.


    SATA III Technical Details

  • • 6 Gb/s raw → ~600 MB/s usable (8b/10b encoding overhead)
  • • Uses 7-pin data connector + 15-pin power connector
  • • Backward compatible with SATA I and SATA II

    • Key Terms

  • • NVMe (Non-Volatile Memory Express) — Protocol optimized for flash storage over PCIe
  • • AHCI (Advanced Host Controller Interface) — Legacy protocol used by SATA
  • • TBW (Terabytes Written) — SSD endurance rating
  • • NAND Flash — Non-volatile memory type used in SSDs
  • • U.2 — Enterprise NVMe connector (2.5-inch form factor)
  • • RAID — Redundant Array of Independent Disks

    • Watch Out For

    > ⚠️ M.2 does not equal NVMe — an M.2 drive can be SATA or NVMe; always check the protocol.

    >

    > ⚠️ SATA III's 6 Gb/s is raw bandwidth — usable throughput is ~550–600 MB/s after encoding.

    >

    > ⚠️ Installing an NVMe drive in an M.2 SATA-only slot will result in the drive not being detected.


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    Power Supply Unit (PSU)


    Key Concepts


    The PSU converts AC wall power to regulated DC voltages used by PC components. Selecting the right wattage and efficiency tier is critical for system stability.


    DC Voltage Rails


    | Voltage | Primary Uses |

    |---|---|

    | +12V | CPU, GPU, motors, PCIe devices |

    | +5V | USB ports, SATA drives, older components |

    | +3.3V | RAM, chipset, some storage |

    | -12V | Legacy serial ports (rarely used) |

    | +5V Standby | Wake-on-LAN, power button detection |


    PSU Connectors


    | Connector | Pins | Powers |

    |---|---|---|

    | ATX Main | 24-pin | Motherboard primary power |

    | EPS12V / CPU | 4-pin or 8-pin | CPU VRM |

    | PCIe | 6-pin | GPU (up to 75W) |

    | PCIe | 8-pin | GPU (up to 150W) |

    | SATA Power | 15-pin | SATA drives and devices |

    | Molex | 4-pin | Older fans, optical drives, some devices |


    > High-end GPUs may require two 8-pin connectors or proprietary 12-pin (12VHPWR) connectors for 300W+ power delivery.


    80 Plus Efficiency Tiers


    | Certification | Efficiency at 50% Load |

    |---|---|

    | 80 Plus (White) | 80% |

    | 80 Plus Bronze | 85% |

    | 80 Plus Silver | 88% |

    | 80 Plus Gold | 90% |

    | 80 Plus Platinum | 92% |

    | 80 Plus Titanium | 94% |


    > Higher efficiency = less wasted energy as heat = lower electricity costs and cooler PSU temperatures.


    PSU Modularity


    | Type | Cable Configuration | Benefit |

    |---|---|---|

    | Non-modular | All cables permanently attached | Lower cost |

    | Semi-modular | Essential cables fixed; others removable | Balance of cost and tidiness |

    | Fully modular | All cables detachable | Best cable management and airflow |


    PSU Troubleshooting


    System powers on briefly then shuts off:

  • • PSU overload protection triggered (underpowered PSU)
  • • Failing capacitor in PSU
  • • Short circuit detected on a rail
  • • Use PSU paperclip test to test PSU independently

    • System won't power on at all:

  • • Check 24-pin and 8-pin CPU connectors
  • • Verify wall outlet and power switch
  • • Test PSU with multimeter or PSU tester

    • Key Terms

  • • VRM (Voltage Regulator Module) — Converts PSU voltage to precise CPU core voltage
  • • Rail — A specific DC voltage output line from the PSU
  • • Capacitor — Energy-storage component; failure causes instability and shutdowns
  • • PFC (Power Factor Correction) — Improves efficiency of AC-to-DC conversion
  • • ATX standard — Specification defining form factor and voltage requirements

    • Watch Out For

    > ⚠️ Always oversize your PSU slightly — running at 100% load reduces efficiency and lifespan. Aim for 50–80% load for best efficiency.

    >

    > ⚠️ The CPU requires BOTH the 24-pin AND the 8-pin connector — missing either will prevent boot.

    >

    > ⚠️ Do not confuse PCIe 6-pin and 8-pin connectors — they look similar but have different power capacities.


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    Expansion Cards & Ports


    Key Concepts


    Expansion cards connect to the motherboard via PCIe (Peripheral Component Interconnect Express) slots, enabling the addition of GPUs, storage controllers, NICs, and

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