Hardware — CPUs and Motherboards

Week of 2026-10-13 · Download .docx

Objectives

Identify CPU socket types and motherboard form factors
Explain POST, beep codes, and CMOS battery function
Describe ESD prevention and proper case airflow

Key terms

POST: Power-On Self-Test — firmware diagnostics run every boot; beep codes signal hardware failures.
CMOS battery: CR2032 coin cell providing standby power for BIOS settings and real-time clock.
LGA: Land Grid Array — Intel socket type where pins are in the motherboard socket.
AM5: AMD's current desktop CPU socket where pins are on the CPU package.
CPU cache: L1/L2/L3 SRAM built near or on the CPU die, storing frequently accessed data.
Thermal paste: Thermal interface material filling micro-gaps between CPU heat spreader and heatsink.
PSU: Power Supply Unit — converts AC wall power to DC voltages (12V, 5V, 3.3V) for components.
ESD: Electrostatic Discharge — static electricity release that can destroy sensitive electronics.
Anti-static strap: Conductive wrist strap grounding the technician to prevent ESD damage.
ATX: Advanced Technology eXtended — standard full-size desktop motherboard form factor.
PCIe x16: 16-lane PCIe slot — primary interface for discrete GPUs and high-bandwidth cards.
UPS: Uninterruptible Power Supply — provides battery backup and surge protection during outages.

The concept

THE CPU AND ITS SOCKET

The CPU socket determines which processors are compatible with a motherboard. Intel uses LGA (Land Grid Array) sockets where the electrical pins are in the motherboard socket and the CPU has flat pads. AMD uses PGA-style sockets where the pins are on the CPU — the current desktop socket is AM5. Mixing Intel CPUs in AMD sockets or vice versa is physically impossible due to different keyways and pin layouts.

POST AND BIOS

Every time you start a computer, the firmware runs POST — testing RAM, GPU, storage, and other components before handing control to the OS. If POST detects a critical failure before video output is available, it generates beep codes through the PC speaker. The CMOS chip stores BIOS settings and runs the real-time clock using a CR2032 coin-cell battery. When this battery dies, the clock resets and BIOS settings return to defaults.

CPU PERFORMANCE

CPU cache is extremely fast SRAM built into the processor die. L1 cache is fastest and smallest; L3 is largest and slowest. Caches hold recently used data and instructions so the CPU does not need to wait for slower DRAM. Thermal throttling occurs automatically when the CPU temperature exceeds its limit — the processor reduces its clock multiplier to generate less heat, protecting itself at the cost of performance.

SAFETY AND AIRFLOW

ESD can permanently damage a CPU, RAM module, or SSD with a discharge too small for humans to feel. An anti-static wrist strap provides a continuous conductive path to ground. Case airflow should follow a front-to-back, bottom-to-top path: cool air enters at the front and bottom; hot air exits at the rear and top, aided by natural convection. Before opening any computer, power it off AND unplug the power cord to remove all standby voltages.

Worked examples

Example 1: A PC powers on but produces one long beep and has no display. Diagnosis: POST detected a GPU or RAM fault. First, reseat the RAM modules one at a time. If the issue persists, try a known-good GPU. Check the BIOS beep code chart for the specific BIOS manufacturer (AMI, Award, Phoenix) to identify the exact component.

Example 2: After installing a new CPU cooler, the system reaches high temperatures under load. Likely cause: insufficient or improperly applied thermal paste. Resolution: Clean the CPU heat spreader and cooler base with isopropyl alcohol, apply a small pea-sized amount of thermal paste to the center of the heat spreader, then reattach the cooler evenly.

Common mistakes

Forgetting to unplug the PSU before working inside the case — standby voltage remains even when powered off.
Touching a CPU or RAM module without an anti-static strap — even small ESD events can cause latent failures.
Applying too much thermal paste — it can spread to socket pins; use a small pea-sized amount.
Confusing LGA (Intel, pins on socket) with AM5 (AMD, pins on CPU) — important for compatibility decisions.
Installing all case fans pointing in the same direction without a defined intake/exhaust path.

Self-check

Try each question before reading the answer. Answers at the bottom of this page.

1. The CMOS battery maintains:

BIOS settings and the real-time clock when power is off
RAM backup power
Laptop battery charge
PCIe slot power

2. ESD is prevented by:

Anti-static wrist strap connected to ground
Rubber gloves
Cotton gloves
Working on carpet

3. Intel CPUs use LGA sockets. AMD desktop CPUs use:

AM5 (pins on CPU)
LGA (same as Intel)
ZIF adapters
BGA (soldered to board)

4. CPU cache stores:

Frequently accessed data closer to CPU to reduce RAM latency
OS kernel permanently
Virtual memory pages
GPU frame buffer

5. Case airflow best practice is:

Intake front/bottom, exhaust rear/top
Intake rear, exhaust front
All fans same direction
All intake at top

Self-check answers

1. A — The CMOS coin-cell battery keeps the BIOS configuration and system clock running when the PC is unplugged.
2. A — An anti-static strap provides continuous grounding to dissipate static charge safely.
3. A — AMD AM5 has pins on the CPU; Intel LGA has pins in the socket — opposite designs.
4. A — Cache is fast SRAM near the CPU holding recently used data to reduce DRAM access latency.
5. A — Front/bottom intake and rear/top exhaust follows natural convection and efficiently removes heat.

Canvas is the official record. This companion enhances the PGCC curriculum; it does not replace it. Last name and class year only. Students with a 504 plan or IEP: your accommodations apply.

↑ Back to top