MSI B760M Mortar BIOS and Buzz | Generated by AI

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Question: MSI MAG B760M Mortar — how to reset/install new BIOS, and is the “滋滋” (buzzing/zizzing) sound when plugging power related?

1. Reset BIOS (clear CMOS)

For the MSI MAG B760M Mortar (DDR4 or DDR5 version), you have three ways:

Method A — Clear CMOS jumper (recommended)

Shut down PC.
Turn off PSU switch (0).
Remove AC power cable.
Press case power button for ~10 seconds (discharge capacitors).
Find the JBAT1 pins on motherboard.
Short the two pins with a screwdriver for ~5–10 seconds.
Reconnect power and boot.

This resets:

XMP memory settings
CPU overclock/undervolt
fan curves
boot order
BIOS settings

Method B — Remove CMOS battery

Power off completely.
Remove the round CR2032 battery.
Wait 5 minutes.
Put battery back.
Boot.

Same result.

2. Install / update new BIOS

MSI boards have M-FLASH and Flash BIOS Button.

Option 1: M-FLASH (normal)

Download BIOS:

MSI MAG B760M Mortar Support Page

Format USB stick as FAT32.
Extract BIOS file.
Copy BIOS file to USB root.
Enter BIOS:

DEL key during boot

Select:

M-FLASH
→ select BIOS file
→ confirm

Do not:

remove power
reset PC
touch USB

Usually takes 5–10 minutes.

Option 2: Flash BIOS Button (even without CPU/RAM)

This is useful if:

motherboard does not POST
CPU unsupported by old BIOS
BIOS corrupted

Steps:

Download BIOS.
Rename file:

Usually MSI requires:

MSI.ROM

Put only that file on FAT32 USB.
Insert into special USB port:

Flash BIOS USB port

Connect:

24-pin motherboard power
8-pin CPU power

Press:

Flash BIOS Button

LED blinking = flashing.

3. About the “滋滋” sound when plugging power

This is interesting.

A small buzzing / zzz sound immediately when PSU power is connected can come from several places.

Case 1: Normal coil whine (possible)

Modern motherboards have:

VRM inductors
standby 5V circuits
capacitors

When AC enters PSU, motherboard gets:

AC 220V
   ↓
PSU standby 5V
   ↓
motherboard standby circuit
   ↓
EC / RGB controller / LAN chip

Some inductors can vibrate:

current → magnetic field → coil vibration → "滋滋"

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A very faint high-frequency sound is usually harmless.

Case 2: PSU issue

More concerning if:

sound comes from PSU itself
crackling
electrical smell
sound changes with GPU load

Example:

Plug AC
 ↓
PSU standby circuit
 ↓
capacitor charging
 ↓
buzz/crackle

A cheap/aging PSU can do this.

Case 3: Short circuit / motherboard problem

Bad signs:

motherboard LED flashes strangely
PSU clicks repeatedly
PC turns on/off loop
burning smell
USB devices behave weirdly

Then disconnect everything:

Only connect:

Motherboard
CPU
CPU cooler
1 RAM stick
PSU

No GPU, no SSD.

Try boot.

4. BIOS reset vs buzzing relationship

Usually:

BIOS corruption
       ❌
       |
       no relation
       |
Power plug buzzing

BIOS is firmware stored in SPI flash.

Buzzing happens in the power delivery analog hardware, not BIOS.

However, if BIOS settings are wrong:

extreme RAM voltage
overclock
unstable CPU voltage

it can cause startup problems, but not usually a buzzing sound when AC is plugged in.

For your specific board + i9-13900KF

You mentioned before you have:

MSI MAG B760M Mortar
Intel i9-13900KF
RTX 4070

This board should support 13900KF, but I would still:

Clear CMOS.
Update latest BIOS.
Load optimized defaults.
Enable XMP only after stable boot.

For a used motherboard, I would also inspect:

VRM area (burn marks)
swollen capacitors
bent CPU socket pins
8-pin CPU power connector

The exact location of the zizz sound matters a lot:

near PSU → PSU suspicion
near CPU VRM → coil whine
near rear I/O → standby circuit

If you record a 5–10 second audio/video clip when plugging AC, the source can usually be identified.

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