RANGER GAMEZ

CompTIA A+ Core 1 (220-1201) · chapter 8 of 15

Week 8: Build day

In this chapter Objectives 3.5, 3.6

  1. Motherboards and connectors
  2. BIOS/UEFI, virtualization and encryption
  3. Power supplies
  4. Practice questions
  5. Chapter recap

Objective 3.5

Motherboards and connectors

Motherboard form factors

Form factor sets size, mounting holes and number of slots, and must match the case and PSU. ATX: 12 x 9.6 in (305 x 244 mm), up to 7 expansion slots. microATX (mATX): 9.6 x 9.6 in (244 x 244 mm), up to 4 slots, fits most ATX cases. Mini-ITX (ITX): 6.7 x 6.7 in (170 x 170 mm), 1 slot, for small PCs like a register.

Three motherboard outlines drawn to scale and stacked from the same corner. ATX is the largest, 305 by 244 mm (12 by 9.6 inches), with up to 7 expansion slots. microATX is 244 by 244 mm (9.6 inches square) with up to 4 slots. Mini-ITX is 170 by 170 mm (6.7 inches square) with 1 slot. A note says smaller boards fit bigger cases, not the other way round.
ATX > microATX > Mini-ITX; a smaller board fits a bigger case.

Exam tip Smaller boards fit bigger cases (mATX in ATX), not the other way around.

Expansion slots: PCI and PCIe

PCI is the old 32-bit shared parallel bus (133 MB/s): legacy cards only. PCIe (PCI Express) uses serial point-to-point lanes: slots come in x1, x4, x8, x16. Each version doubles per-lane speed: PCIe 3.0 ~1 GB/s, 4.0 ~2 GB/s, 5.0 ~4 GB/s per lane per direction. A smaller card works in a bigger slot (x1 card in x16 slot).

Expansion slots drawn to scale as seen from above. PCIe x1 is the shortest, about 25 mm; PCIe x4 about 39 mm; PCIe x8 about 56 mm; PCIe x16 about 89 mm with a retention latch, used for the graphics card. Every PCIe slot has the same short first section before a key gap. Last is a white legacy PCI slot: the old 32-bit shared parallel bus. A note says a smaller card works in a bigger slot.
PCIe slot length = lane count: x1, x4, x8, x16. A small card fits a big slot.

Exam tip Video cards go in the x16 slot wired to the CPU (usually the top one).

Storage connectors: SATA, eSATA, M.2

Boards have several SATA 7-pin ports for drives and optical drives (6 Gbps each). Some older boards have an eSATA port on the rear panel for external drives. M.2 slots take NVMe/SATA SSDs (and Wi-Fi cards in E-key slots). Using some M.2 slots can disable SATA ports that share lanes: check the manual.

The back edge of a 2.5-inch SATA drive showing two L-shaped connectors side by side: the wide 15-pin SATA power connector and the narrow 7-pin SATA data connector. Labels: SATA power carries 3.3, 5 and 12 volts; SATA III data runs at 6 Gbps. Below, an eSATA port: a straight, shielded connector with no L-shape and no power pins.
Every SATA drive takes two cables: wide 15-pin power and narrow 7-pin data.

Exam tip SATA drive missing after adding an M.2 SSD? The M.2 slot may share lanes with that SATA port.

Power connectors and headers

Power connectors on the board: 24-pin ATX main power and 4/8-pin ATX12V (EPS) CPU power near the socket. Headers are pin rows for case cables: front panel (power switch, reset, power and drive LEDs), USB 2.0/3.x front ports, front audio, fan headers (3-pin DC, 4-pin PWM), RGB lighting, and TPM.

Schematic ATX motherboard with numbered parts and a legend. 1: rear I/O panel at the back edge. 2: CPU socket. 3: 8-pin CPU power (EPS12V) near the socket at the top edge. 4: DIMM memory slots beside the socket. 5: 24-pin ATX main power on the right edge. 6: CPU_FAN header. 7: PCIe x16 slot. 8: PCIe x1 slot. 9: M.2 slot between the PCIe slots. 10: chipset. 11: SATA ports on the right edge. 12: CMOS battery. 13: front-panel header (power switch, reset, LEDs) on the bottom edge. 14: USB headers.
Know where things live: socket, DIMMs, power plugs, slots, SATA and the front-panel header.

Exam tip Front power button does nothing? Check the front-panel header pins (PWR_SW) first.

CPU sockets and compatibility

The CPU must match the board's socket and chipset. Intel uses LGA (land grid array): the pins are in the socket on the board (e.g. LGA 1700, LGA 1851). AMD used PGA for AM4 (pins on the CPU) and moved to LGA with AM5. Multisocket boards hold two or more CPUs: servers and high-end workstations. A BIOS update may be needed for a newer CPU on the same socket.

Side views of two CPU socket types. LGA, land grid array: the CPU has flat gold pads underneath and the springy pins are in the motherboard socket; used by Intel and by AMD AM5. PGA, pin grid array: the pins stick out of the bottom of the CPU and drop into holes in the socket; used by AMD AM4. A note says bent pins are in the board socket on LGA, and on the CPU on PGA.
LGA: pins in the socket. PGA: pins on the CPU.

Exam tip Bent pins: on LGA they are in the board socket; on PGA they are on the CPU.

Check yourself 1After you add an M.2 SSD to the workstation, one SATA drive disappears. Its cable is fine. What is the MOST likely cause?

  1. The power supply can't run both drives at once
  2. The M.2 slot shares lanes with that port
  3. SATA drives stop working when UEFI mode is on
  4. The new SSD needs a separate 8-pin EPS cable
Show the answer

Answer: B. The M.2 slot shares lanes with that port

On many boards, using some M.2 slots disables SATA ports that share the same lanes. The manual lists which ports turn off; move the drive to another port.

CPU architecture and core configurations

x86 is 32-bit; x64 (x86-64) is 64-bit and can use far more than 4 GB of RAM. Desktops and most laptops are x64. ARM is a RISC design: power-efficient, used in phones, tablets and a growing number of laptops; apps must be built for ARM or emulated. Core configurations: multicore (several cores per CPU), hyper-threading/SMT (2 threads per core), and hybrid designs with performance and efficiency cores.

Exam tip 32-bit OS sees about 4 GB of RAM max. Need more? x64 CPU and OS.

Expansion cards

Video card (GPU): extra display outputs and 3D/compute power; often needs 6/8-pin or 16-pin PCIe power. Sound card: better audio, more channels. Capture card: records video from cameras or consoles (HDMI in) for streaming and editing. NIC card: adds or upgrades networking (10 GbE, fiber SFP+, extra ports). Install the driver after the card.

Exam tip Marketing wants to record a camera's HDMI output on the PC = capture card.

Cooling

A heat sink draws heat from the CPU through metal fins. Thermal paste fills tiny gaps between CPU and heat sink (pea-size dot, reapply if removed). Thermal pads do the same for VRMs, memory and SSDs, often in laptops. Fans move air: front intake, rear/top exhaust. Liquid cooling (often an AIO: pump, tubes, radiator) moves heat to a radiator; check the pump and leaks.

Left: a cross-section of CPU cooling from bottom to top: the CPU in its socket, a thin layer of thermal paste, a metal heat sink with fins, and a fan blowing air through the fins. Right: a PC case seen from the side, with cool air pulled in by front intake fans and warm air pushed out by rear and top exhaust fans.
Paste fills the gaps, the heat sink spreads heat, fans move it out of the case.

Exam tip Reused a heat sink without new paste? Expect overheating and throttling.

Objective 3.5

BIOS/UEFI, virtualization and encryption

BIOS vs. UEFI and boot options

UEFI replaced legacy BIOS: mouse-driven menus, GPT disks over 2 TB, faster boot, Secure Boot. Settings live in flash; a CMOS battery keeps the clock. Boot options set the boot order (SSD, USB, network/PXE) and UEFI vs. legacy (CSM) mode. USB permissions can disable USB ports or USB boot so nobody boots another OS from a flash drive.

UEFI SETUP > Boot
 Boot Mode ........ [UEFI]
 Boot Option #1 ... [Windows Boot Manager]
 Boot Option #2 ... [UEFI: USB Drive]
 Network (PXE) .... [Disabled]
 USB Boot ......... [Disabled]
 Secure Boot ...... [Enabled]
Diagram of startup. Power on, then POST, the power-on self-test, then the firmware works down the boot order list: 1 Windows Boot Manager on the SSD, 2 a UEFI USB drive, 3 network PXE boot. The first bootable device found starts. A side note says to boot an installer from USB, enable USB boot and move it up the list, and that USB boot can be disabled to stop people booting another OS.
Firmware tries each boot option in order; the first bootable one wins.

Exam tip To boot an installer from USB, enable USB boot and move it up the boot order.

Passwords, Secure Boot and TPM features

A BIOS (supervisor/admin) password is needed to change firmware settings. A boot (user/power-on) password is needed to start the computer at all. Secure Boot (UEFI) only runs bootloaders signed with trusted keys, blocking boot-level malware (rootkits). TPM security features are switched on in firmware (often "PTT" on Intel, "fTPM" on AMD) for BitLocker and Windows 11.

Exam tip Stop users changing boot order = BIOS/supervisor password. Stop anyone booting the PC = boot password.

Fans and temperature monitoring

Firmware shows temperature monitoring for CPU and system, fan speeds and voltages, and can set alarms or shutdown thresholds. Fan considerations: choose fan curves (silent vs. performance), set which header is the CPU fan (some boards refuse to boot or warn with no CPU fan detected), and PWM vs. DC control.

Exam tip "CPU Fan Error" at boot: fan not plugged into CPU_FAN, or fan failed.

Check yourself 2You reuse the old heat sink on a new CPU. Now the PC runs hot and slows itself down. What was MOST likely skipped?

  1. Enabling Secure Boot
  2. Moving the CPU fan cable to SYS_FAN
  3. Installing a capture card
  4. Applying new thermal paste
Show the answer

Answer: D. Applying new thermal paste

Thermal paste fills tiny gaps between the CPU and the heat sink. A reused heat sink without fresh paste moves heat poorly, so the CPU overheats and throttles.

Virtualization support

Running VMs well needs CPU hardware virtualization enabled in firmware: Intel VT-x or AMD-V (SVM), plus SLAT (EPT/RVI). VT-d/AMD-Vi (IOMMU) lets a VM use a physical device directly. Often disabled by default; a hypervisor will refuse to start VMs until you enable it.

Exam tip Hypervisor says "virtualization not available"? Enable VT-x/AMD-V in UEFI.

Encryption hardware: TPM and HSM

A TPM (Trusted Platform Module) is a chip (or firmware) on the motherboard that stores encryption keys, measures the boot process, and unlocks full-disk encryption like BitLocker only if the system has not been tampered with. Windows 11 requires TPM 2.0. An HSM (hardware security module) is a separate device or card that creates, stores and uses many keys at high speed: for servers, certificate authorities and payments.

Exam tip One PC's disk encryption key = TPM. Thousands of keys for a payment server = HSM.

Objective 3.6

Power supplies

Input voltage

Wall power is AC. North America uses 110-120 VAC (60 Hz); much of Europe/Asia uses 220-240 VAC (50 Hz). Most PSUs are auto-switching (100-240 V). Some older PSUs have a manual voltage selector switch: set 115 V and plug into 230 V and you can destroy the PSU.

Exam tip Taking a PC abroad? Check the label for 100-240 V; only change the plug if so.

Output rails: 3.3 V, 5 V, 12 V

The PSU converts AC to DC rails. 12 V: the heavy lifter for CPUs, GPUs, fans, drive motors. 5 V: USB, drive logic, older parts. 3.3 V: chipsets, RAM and some M.2/PCIe parts. Molex gives 12 + 5 V; SATA power adds 3.3 V.

Wire color  Voltage
Yellow      +12 V
Red         +5 V
Orange      +3.3 V
Black       Ground
Four colored wires from a power supply with their voltages and what they feed. Yellow is +12 volts: CPUs, graphics cards, fans and drive motors, the heavy lifter. Red is +5 volts: USB and drive logic. Orange is +3.3 volts: chipset, RAM and some M.2 and PCIe parts. Black is ground. A note says Molex carries 12 and 5 volts, and SATA power adds 3.3 volts.
Yellow 12 V does the heavy work; red is 5 V, orange 3.3 V, black ground.

Exam tip Most power in a modern PC is on the 12 V rail. Compare its amp rating when sizing for a GPU.

20+4 pin connector, modular and redundant PSUs

The main 20+4 pin connector fits modern 24-pin boards, and the 4 pins detach for older 20-pin boards. A modular PSU lets you attach only the cables you need: better airflow, tidier builds (semi-modular has the main cables fixed). A redundant PSU setup has two or more hot-swappable units in a server; if one fails, the other carries the load.

Face-on drawings of five power supply connectors. The 24-pin ATX main connector, two rows of 12, split as 20 plus a detachable 4, powers the motherboard. The 8-pin EPS12V CPU connector, split 4 plus 4, sits near the CPU socket. The 6+2-pin PCIe connector powers graphics cards. The 15-pin SATA power connector is flat and L-shaped and feeds drives with 3.3, 5 and 12 volts. The 4-pin Molex connector has four round pins in a row with two clipped corners, giving 12 and 5 volts to older drives and fans.
Match each plug to its job: 24-pin board, 8-pin CPU, 6+2 GPU, SATA drives, Molex legacy.

Exam tip Server must stay up when a PSU dies = redundant hot-swap power supplies.

Wattage and energy efficiency

Add up component power (CPU TDP, GPU board power, drives, fans) and add 20-30% headroom. Too small = random shutdowns under load. Energy efficiency is shown by the 80 PLUS rating: an efficient PSU wastes less power as heat.

80 PLUS (115 V)  20%  50%  100%
Bronze           82%  85%  82%
Gold             87%  90%  87%
Platinum         90%  92%  89%
Titanium *       92%  94%  90%
* also 90% at 10% load

Exam tip Wattage is the max it can supply; the PC draws only what it needs.

Check yourself 3Priya wants nobody to be able to change the boot order on the register PCs, but staff must still be able to turn them on without a password. What should you configure?

  1. A boot (power-on) password
  2. A BIOS (supervisor) password
  3. Secure Boot with a new signing key
  4. A TPM PIN for BitLocker
Show the answer

Answer: B. A BIOS (supervisor) password

The supervisor/BIOS password protects the firmware settings only; the PC still boots normally.

Practice questions

Answer in your head, then open the answer. Ranger's Help Desk has 436 questions like these for A+ Core 1, with mock exams.

Question 1A customer wants a very small home theater PC that fits under a TV. Which motherboard form factor fits BEST?

  1. microATX
  2. ITX
  3. ATX
  4. Multisocket server board
Show the answer

Answer: B. ITX

ITX boards (such as mini-ITX, 17 x 17 cm) are the smallest of the three and fit compact cases.

Question 2A technician has a microATX motherboard and a full-size ATX case. Will the board fit?

  1. Yes, it uses a subset of the ATX mounting holes
  2. Only with an ITX adapter plate
  3. No, microATX needs a microATX case
  4. Only if the case has a power supply with a 20-pin connector
Show the answer

Answer: A. Yes, it uses a subset of the ATX mounting holes

microATX is a smaller version of ATX and lines up with ATX standoff positions. A full ATX board will not fit a microATX case, though.

Question 3A customer wants to move an old 32-bit PCI sound card into a new motherboard that has only PCIe and M.2 slots. What should the technician tell the customer?

  1. It will work in a PCIe x1 slot with no adapter or driver
  2. It can be installed in the M.2 slot
  3. It will work in a PCIe x16 slot
  4. It will not fit; a PCIe or USB audio device is needed
Show the answer

Answer: D. It will not fit; a PCIe or USB audio device is needed

Legacy PCI and PCIe use different slots and signaling. A PCI card needs a PCI slot, so a newer device is the practical fix.

Question 4After building a PC, the technician finds that the case's power button and front USB ports do nothing. Where should these cables be connected?

  1. eSATA ports
  2. Unused PCIe x1 slot
  3. M.2 socket
  4. Motherboard headers
Show the answer

Answer: D. Motherboard headers

Front-panel switches, LEDs, USB and audio connect to pin headers on the motherboard. The manual shows each header's pinout.

Question 5A technician installs an M.2 SSD in the second M.2 slot. Afterward, a SATA hard drive that was working disappears. Based on the exhibit, what is the cause?

  1. Secure Boot disabled the SATA controller
  2. The M.2 SSD has a different DDR type
  3. M.2_2 shares bandwidth with SATA5 and SATA6
  4. The SATA drive now needs a Molex power connector
Show the answer

Answer: C. M.2_2 shares bandwidth with SATA5 and SATA6

The manual notes that using M.2_2 disables SATA5/SATA6. Moving the hard drive to SATA1-4 will bring it back.

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