X79 + Xeon E5-2690 freezes when enabling more than 4 physical cores on Linux Mint 22.3

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Title:

X79 + Xeon E5-2690 – System freezes when enabling more than 4 physical cores (Mint 22.3, kernel 6.14)

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Post:

Hi everyone,

I’m troubleshooting a strange SMP issue on an X79 system and would appreciate some guidance.

Hardware:

•	Motherboard: X79 (American Megatrends BIOS 2.10.1208, 2013)

•	CPU: Intel Xeon E5-2690 (8 cores / 16 threads)

•	GPU: NVIDIA GTX 1070

•	Storage: SATA SSD (Patriot Torch)

•	Linux Mint 22.3 Cinnamon

•	Kernel: 6.14.0-37-generic

•	intel-microcode installed and confirmed loading early

Problem:

The system freezes during boot whenever I enable more than 4 physical cores in BIOS.

Behavior is very consistent:

•	1 core → boots

•	2 cores → boots

•	4 cores → boots

•	4 cores + Hyper-Threading (8 logical CPUs) → boots

•	6 cores → freezes during boot

•	8 cores → freezes during boot

The freeze happens after USB/SATA initialization, before graphical login. Screen goes black/gray and system is unresponsive (no TTY access).

Important observations:

•	Microcode update confirmed:

microcode: Updated early from: 0x00000710

•	HT works fine on 4 cores (8 logical CPUs total)

•	This suggests interrupt routing is functional for 8 logical CPUs

•	Only additional physical cores (above 4) cause freeze

What I’ve tried:

•	Fresh install

•	intel-microcode installed

•	Removed quiet splash

•	acpi=off

•	noapic

•	nolapic

•	irqpoll

•	maxcpus=2

•	nox2apic

•	Disabled C-states

•	Disabled SpeedStep (EIST)

•	HT off (for physical core testing)

None allow 6 or 8 physical cores to boot.

Given that HT works but additional physical cores do not, this seems like either:

•	APIC ID / topology issue in BIOS

•	Power ramp / VRM issue during full SMP bring-up

•	Kernel 6.x + X79 firmware interaction

Has anyone successfully run all 8 cores on X79 + Xeon E5 v1 under recent kernels?

Would testing a 5.15 LTS kernel be recommended?

Appreciate any help