Question Weirdly unstable PC after every cold boot

[mariushh]

Hello, I’ve recently built a PC for my friend with the following specs:

• CPU: AMD Ryzen 7 9700X
• Motherboard: Gigabyte B650 Gaming X AX V2 (BIOS version F36)
• GPU: Gigabyte Windforce RTX 5070 12GB
• RAM: Kingston Fury Beast DDR5 RGB 6000MHz CL30 (2x16GB)
• Cooler: Cooler Master MasterLiquid 240 Core ARGB
• PSU: Cooler Master MWE Gold 750 V2 ATX 3.1
• Storage: Kingston NV3 M.2 NVMe 2TB
• Case: NZXT H2 Flow RGB
• OS: Windows 11 Pro x64 (fully updated)

LAN not working on first boot​

Initially, everything seemed fine — CPU and GPU temperatures were normal during gaming (tested in Clair Obscur).
However, after shutting down the PC and turning it back on the next day, the motherboard suddenly wouldn’t detect the LAN cable at all.


I have:

• Installed the latest LAN driver and all other drivers from the official Gigabyte site.
• Changed BIOS settings (disabled Fast Boot, disabled Network Stack, disabled ERP Ready, changed Restore AC Power Loss setting) — no effect.
• Updated BIOS to version F36.
• Cleared CMOS.
• Reset network settings multiple times.
• Disabled Turn on fast startup in Windows power options.

None of this fixed it. The strange part:
If I turn off the power strip (fully cutting power) for a few seconds and then turn it back on, the LAN works normally.
It seems that after a cold boot with power still connected, the motherboard sometimes fails to initialize the LAN module — but a PSU switch-off for 5 seconds always fixes it.

High CPU temps until reset​

Later, another issue appeared. On some boots, the PC spins all fans at high speed immediately, and in HWinfo64 the CPU temperature reads 90°C+ at idle. The system freezes or becomes extremely sluggish(despite the fact that CPU usage is almost 0).
But when I check in BIOS right after boot, the CPU temp is normal (around 39–44°C).

Behavior:

• Sometimes 1 reset fixes it, sometimes it takes 3–5 resets, or waiting 5 minutes after boot.
• Once it stabilizes, the PC can run for 10+ hours under heavy load (gaming) with completely normal temperatures and no crashes.
• Issue happens only during initial boot, never while running.

What I’ve tried for the temperature issue:​

• Reseated CPU and RAM — no change.
• Checked cooler mount and paste application — no change.
• Verified pump and fan headers are connected correctly.

This is my first AMD build (I usually work with Intel), but I’m confident in my assembly process.

I’m attaching two screenshots — in one, the system boots normally (LAN is detected, temperatures are normal), and in the other, you can see the issue I described above.
Right now I’m out of ideas — any help or suggestions would be appreciated.

After making this post i also fresh installed Windows, at first everything was good, but of course after another cold start the issues came back 🙁

 

[NightHawkRMX]

I would suspect a faulty motherboard. You should still be well within your warranty from gigabyte, id see about an RMA.

 

[MasterBlaster22]

Hello, I’ve recently built a PC for my friend with the following specs:

• CPU: AMD Ryzen 7 9700X
• Motherboard: Gigabyte B650 Gaming X AX V2 (BIOS version F36)
• GPU: Gigabyte Windforce RTX 5070 12GB
• RAM: Kingston Fury Beast DDR5 RGB 6000MHz CL30 (2x16GB)
• Cooler: Cooler Master MasterLiquid 240 Core ARGB
• PSU: Cooler Master MWE Gold 750 V2 ATX 3.1
• Storage: Kingston NV3 M.2 NVMe 2TB
• Case: NZXT H2 Flow RGB
• OS: Windows 11 Pro x64 (fully updated)

LAN not working on first boot​

Initially, everything seemed fine — CPU and GPU temperatures were normal during gaming (tested in Clair Obscur).
However, after shutting down the PC and turning it back on the next day, the motherboard suddenly wouldn’t detect the LAN cable at all.


I have:

• Installed the latest LAN driver and all other drivers from the official Gigabyte site.
• Changed BIOS settings (disabled Fast Boot, disabled Network Stack, disabled ERP Ready, changed Restore AC Power Loss setting) — no effect.
• Updated BIOS to version F36.
• Cleared CMOS.
• Reset network settings multiple times.
• Disabled Turn on fast startup in Windows power options.

None of this fixed it. The strange part:
If I turn off the power strip (fully cutting power) for a few seconds and then turn it back on, the LAN works normally.
It seems that after a cold boot with power still connected, the motherboard sometimes fails to initialize the LAN module — but a PSU switch-off for 5 seconds always fixes it.

High CPU temps until reset​

Later, another issue appeared. On some boots, the PC spins all fans at high speed immediately, and in HWinfo64 the CPU temperature reads 90°C+ at idle. The system freezes or becomes extremely sluggish(despite the fact that CPU usage is almost 0).
But when I check in BIOS right after boot, the CPU temp is normal (around 39–44°C).

Behavior:

• Sometimes 1 reset fixes it, sometimes it takes 3–5 resets, or waiting 5 minutes after boot.
• Once it stabilizes, the PC can run for 10+ hours under heavy load (gaming) with completely normal temperatures and no crashes.
• Issue happens only during initial boot, never while running.

What I’ve tried for the temperature issue:​

• Reseated CPU and RAM — no change.
• Checked cooler mount and paste application — no change.
• Verified pump and fan headers are connected correctly.

This is my first AMD build (I usually work with Intel), but I’m confident in my assembly process.

I’m attaching two screenshots — in one, the system boots normally (LAN is detected, temperatures are normal), and in the other, you can see the issue I described above.
Right now I’m out of ideas — any help or suggestions would be appreciated.

After making this post i also fresh installed Windows, at first everything was good, but of course after another cold start the issues came back 🙁

I would suggest checking the power draw to your VRMs and also comparing it to the power draw from the CPU under different loads. There you will find your culprit.