PC Hardware Components Guide

The CPU is the brain of the computer. It fetches instructions from memory, decodes them, executes them, and writes results back. Every action the computer performs — running software, processing files, responding to input — is ultimately executed by the CPU.

Key CPU specifications: clock speed (GHz) — how many instruction cycles per second; cores — independent processing units within the chip (quad-core = 4 cores running in parallel); threads — virtual cores via hyper-threading (a 4-core/8-thread CPU can run 8 concurrent threads); cache (L1/L2/L3) — fast on-chip memory storing recently used data.

Major CPU manufacturers: Intel (Core i3/i5/i7/i9 for consumer; Xeon for servers) and AMD (Ryzen 3/5/7/9 for consumer; EPYC for servers). Intel uses LGA (Land Grid Array) sockets; AMD uses PGA (Pin Grid Array) or AM5 LGA sockets. CPU and motherboard sockets must be compatible — you cannot install an Intel CPU in an AMD motherboard.

RAM is the computer's short-term working memory. The OS, running applications, and actively-used data are loaded into RAM because it is far faster than storage (nanosecond access vs millisecond). RAM is volatile — its contents are lost when power is removed.

Current RAM types: DDR4 is the most common in systems from 2016–2023. DDR5 is the current generation (Intel 12th gen+, AMD Ryzen 7000+). DDR generations are not backward-compatible — DDR4 sticks cannot be installed in DDR5 slots. RAM sticks also have physical notches (keys) in different positions to prevent wrong installation.

Form factors: DIMM (Dual In-Line Memory Module) for desktops — full-length sticks. SO-DIMM (Small Outline DIMM) for laptops and small-form-factor PCs — about half the length. Speed is measured in MHz (DDR4-3200 runs at 3200 MHz effective) or as PC rating (PC4-25600 = DDR4-3200).

The GPU handles graphics rendering — converting 3D scene data into the 2D pixels displayed on your monitor. Modern GPUs contain thousands of small cores optimised for parallel processing, making them also excellent for AI/ML training, video encoding, and scientific computing.

Discrete GPU: a dedicated graphics card installed in a PCIe x16 slot, with its own VRAM (Video RAM — typically 8–24 GB). Discrete GPUs from NVIDIA (GeForce) and AMD (Radeon) are required for gaming, video editing, and 3D work. NVIDIA also produces professional cards (Quadro/RTX Pro) for workstations.

Integrated GPU: built into the CPU die (Intel HD/UHD/Iris Xe, AMD Radeon Graphics). Uses system RAM rather than dedicated VRAM. Sufficient for office work, web browsing, and 4K video playback, but not for gaming or GPU compute workloads. Most Intel Core processors include integrated graphics; AMD calls this an APU (Accelerated Processing Unit).

Display outputs on modern GPUs: HDMI (most common for monitors and TVs), DisplayPort (preferred for high refresh rate monitors), USB-C/Thunderbolt (on laptops), and legacy DVI/VGA (older systems). Multiple monitors can be connected if the GPU has multiple outputs.

The PSU converts the 120V/240V AC power from the wall outlet into the DC voltages PC components require: +12V (primary rail — powers CPU, GPU, storage motors), +5V (USB, older drives, logic circuits), and +3.3V (RAM, CPU I/O).

Wattage is the PSU's total power output capacity. The PSU must supply enough watts for all components simultaneously under full load. A gaming PC with a high-end GPU might need a 750W–1000W PSU; an office PC might need only 300W. Undersized PSUs cause random shutdowns, instability under load, or refusal to POST.

The 80 Plus certification rates PSU efficiency — the percentage of AC power converted to DC (the rest becomes heat). Bronze = 82–85% efficient; Gold = 87–90%; Platinum = 90–92%; Titanium = 94%+. Higher efficiency means less wasted heat and lower electricity bills. The certification is printed on the PSU label.

Modular vs non-modular: a modular PSU lets you attach only the cables you need, reducing cable clutter inside the case. Non-modular PSUs have all cables permanently attached.

The motherboard is the central hub that physically connects and allows communication between every other component. It contains the CPU socket, RAM slots, PCIe slots (for GPU and expansion cards), M.2 slots (for NVMe SSDs), SATA connectors (for drives), USB headers, and the chipset that manages data flow between components.

Form factors define the physical size and mounting hole pattern: ATX (standard full-size, 305×244mm) fits in full-tower and mid-tower cases; Micro-ATX (244×244mm) is smaller; Mini-ITX (170×170mm) is the smallest common form factor for compact builds.

The chipset (Intel: Z790, B760; AMD: X670, B650) determines which CPU generations are supported, how many PCIe lanes are available, and which features are unlocked (CPU overclocking is typically only available on Intel Z-series and AMD X-series chipsets).

The PCIe (Peripheral Component Interconnect Express) bus is the high-speed interface for GPUs, NVMe SSDs, and expansion cards. PCIe x16 slots (full bandwidth) are used for GPUs; PCIe x4 and x1 slots are used for other expansion cards. PCIe 4.0 doubles the bandwidth of PCIe 3.0; PCIe 5.0 doubles it again.

HDD (Hard Disk Drive) — uses spinning magnetic platters and a moving read/write head. Sequential read speeds of ~150 MB/s. Susceptible to physical shock (the read head can crash into the platter). Failure symptoms: clicking or grinding sounds, S.M.A.R.T. errors, slow read/write, bad sectors. HDDs are still cost-effective for bulk storage (e.g., NAS drives, backup drives).

SSD (Solid-State Drive) using the SATA interface — no moving parts; uses flash memory chips. Sequential read speeds of ~550 MB/s. Installs in a 2.5" bay or adapts to a 3.5" bay. Uses the same SATA cable as HDDs. The primary reason for upgrading from an HDD to an SSD is dramatically faster boot times and application load times.

NVMe SSD (Non-Volatile Memory Express) using the M.2 connector — plugs directly into a motherboard M.2 slot (no cables). Speeds of 3,500–7,000+ MB/s. Far faster than SATA SSD because NVMe uses the PCIe bus rather than the SATA interface. M.2 slots can accept either SATA or NVMe drives depending on the slot — check the motherboard spec before buying.