Almost every IT support task eventually touches the hardware inside a computer. This lesson is a guided tour — what each part does, what variants exist, and what a technician needs to recognise on sight.
The Motherboard
The motherboard is the large printed circuit board that everything else plugs into. Its main components:
- CPU socket: Holds the processor. Common Intel sockets: LGA 1700, LGA 1851. AMD: AM4, AM5.
- RAM slots (DIMM slots): Usually 2 or 4. Modern systems use DDR4 or DDR5.
- PCIe slots: For expansion cards (GPU, NVMe via adapter, capture cards). PCIe 4.0 and 5.0 are current.
- M.2 slots: For NVMe SSDs — small, fast storage modules.
- SATA ports: For 2.5"/3.5" SSDs and HDDs.
- Chipset: The "traffic controller" connecting CPU to slower components. Intel Z/B/H series; AMD X/B series.
- BIOS/UEFI chip: Firmware that runs at boot.
- CMOS battery: CR2032 coin cell that keeps BIOS settings + clock when powered off.
- Front-panel headers: Tiny pins where the case's power button, LEDs, USB, and audio plug in.
Form factors
| Form factor | Size | Typical use |
|---|---|---|
| ATX | 305 × 244 mm | Desktops, gaming PCs |
| Micro-ATX | 244 × 244 mm | Office desktops |
| Mini-ITX | 170 × 170 mm | Small form factor / HTPC |
The CPU
The Central Processing Unit executes the instructions that make a computer do anything. Key specs a technician should recognise:
- Cores: Independent execution units. Modern consumer CPUs have 6-24 cores.
- Threads (hyperthreading / SMT): Logical cores; often 2× physical cores.
- Clock speed: Base GHz and boost GHz.
- Cache: L1, L2, L3 — tiny, fast memory on the CPU die. Bigger = better.
- TDP (Thermal Design Power): Heat output in watts; determines cooler needed.
- Integrated graphics: Many CPUs include a GPU; useful for offices without discrete GPUs.
- Architecture: Intel "Core Ultra" / "Raptor Lake"; AMD "Zen 4 / 5"; Apple "M3/M4"; Qualcomm "Snapdragon X" (ARM Windows).
Installing a CPU (key safety steps)
- Ground yourself — anti-static wrist strap or touch the case.
- Lift the socket lever; orient CPU using the gold triangle to match the socket.
- Drop in straight — never force.
- Apply thermal paste (pea-sized drop).
- Mount the cooler and connect its fan to CPU_FAN header.
Memory (RAM)
RAM is volatile — content lost on power-off. It holds running programs and OS structures.
| Type | Speeds | Notes |
|---|---|---|
| DDR4 | 2133-3600 MT/s | Still common; cheaper |
| DDR5 | 4800-8000+ MT/s | Current generation; required on newer platforms |
| SODIMM | Smaller form factor | Laptops and Mini-PCs |
| ECC | Adds parity | Servers, workstations — catches bit errors |
Dual / quad channel: Installing matched pairs in the right slots (often A2 + B2) doubles memory bandwidth. Always check the motherboard manual.
Storage
Hard Disk Drives (HDDs)
- Spinning magnetic platters
- Cheap per TB; up to 22+ TB capacities
- Speeds: 5400 / 7200 / 10000 / 15000 RPM
- SATA interface (6 Gb/s)
- Sensitive to shock; loud-ish; slow random reads
Solid State Drives (SSDs)
| SSD type | Interface | Typical speed |
|---|---|---|
| 2.5" SATA SSD | SATA III | ~550 MB/s |
| M.2 SATA | SATA via M.2 slot | ~550 MB/s |
| M.2 NVMe (PCIe 3.0) | PCIe x4 | ~3,500 MB/s |
| M.2 NVMe (PCIe 4.0) | PCIe x4 | ~7,000 MB/s |
| M.2 NVMe (PCIe 5.0) | PCIe x4 | ~14,000 MB/s |
SSDs are the default for OS drives in any new system. Mechanical HDDs are now mostly bulk/archival.
The Power Supply Unit (PSU)
- Converts AC mains to DC voltages (+3.3V, +5V, +12V) the system needs
- Wattage rating: 450W is fine for office; 750-1000W for high-end gaming
- 80 PLUS rating (Bronze / Gold / Platinum) = efficiency
- Modular vs non-modular: modular has detachable cables for cleaner builds
- Key connectors: 24-pin ATX (motherboard), 8-pin EPS (CPU), 6+2-pin PCIe (GPU), SATA power, Molex (legacy)
Safety: Never open a PSU. Even unplugged, capacitors hold dangerous charge.
Cooling
- Air cooling: Heatsink + fan on CPU; case fans for airflow (intake at front, exhaust at rear/top)
- Liquid cooling: AIO (all-in-one) coolers — pump, tubes, radiator; quieter at high loads
- Thermal paste: Between CPU and cooler; reapply every few years or after removing the cooler
Graphics Cards (GPUs)
- Plugs into a PCIe x16 slot
- Has its own VRAM (4-24 GB GDDR6/GDDR6X)
- Needs supplementary power: 6/8-pin PCIe or 12VHPWR connector
- Outputs: HDMI, DisplayPort (most common), occasional USB-C
- Major brands: NVIDIA (GeForce RTX), AMD (Radeon RX), Intel (Arc)
Expansion Cards You May Still See
- NIC (network interface card) — only if motherboard NIC is broken/limited
- Wi-Fi / Bluetooth M.2 card or PCIe card
- Sound cards — increasingly rare
- USB / Thunderbolt expansion cards
- RAID / SAS HBA controllers — workstations and servers
BIOS and UEFI
UEFI (Unified Extensible Firmware Interface) is the modern replacement for the legacy BIOS. It runs before the OS and is where you configure boot order, enable virtualisation, set RAID modes, enable Secure Boot, and view CPU temps. Press Del / F2 / F10 at boot to enter.
Compatibility Quick Checklist
Before recommending or installing parts, verify:
- Does the CPU match the motherboard socket?
- Does the motherboard need a BIOS update for that CPU?
- Is the RAM the right type (DDR4 vs DDR5) and on the motherboard's QVL?
- Does the PSU have the connectors and watts you need?
- Will the GPU fit the case (length) and cooler fit (height)?
- Does the OS support the storage interface (very old Windows can't boot from NVMe without an updated installer)?
You now know enough to identify and discuss every major component inside a PC. The next lesson moves up the stack to operating systems.