FCH Spread Spectrum, PCIe 5.0 & GPU Instability

Ever since I upgraded my gaming pc to a PCIe 5 capable video card (5080 FE) I have had infrequent but deeply annoying instability issues when booting the pc. A reboot would fix, but the problem would not go away, after months of troubleshooting I finally found a fix.

The Hardware#

I should start by detail the hardware that is in use, I think this will mostly likely apply to any modern hardware where the motherboard has PCIe 5 and a GPU is running (or trying to) in 5 mode. However it could be limited to particular motherboard chipsets or GPUS so any detail here may help others.

The Problems#

In about (approximately) 1 in 6 times of booting the computer (cold start) the following symptoms would present themselves.

• Erratic or slow mouse movement
• Laggy UI
• Exceptionally poor GPU performance, sub 30 fps on furmark
• If continued GPU stress the system would lock

This was always resolved by a reboot and never returned until the computer was turned off and then back on (given the 1 in roughly 6 chance).

Attempted Fixes#

This problem had persisted for many months so lots of different tweaks were tried to resolve this.

• Bios updates, always keeping up to date with the latest MSI bios
• Nvidia driver updates, driver rollbacks, beta drivers
• Nvidia firmware updates
• Disabling onboard GPU
• Disabling fast startup (in windows)
• Changing memory timing
• Full bios reset
• Full windows install
• Different primary NVME
• Forcing PCIe 4x mode on GPU in bios

None of these worked, and then one day I stumbled on a MSI forum post detailing people having the same or very similar issues.

The Solution#

FCH Spread Spectrum Control, turn it on!

Bios options will vary but there should be an option somewhere in the bios for it. Turning it on for me made the instability go away. It has been months now and I have not had a repeat of the problem.

What is FCH Spread Spectrum Control?#

Put simply it is a method to vary the base clock frequency to reduce electromagnetic interference (EMI). This is often turned off if people are overclocking their CPU as you want a stable known base clock speed. However if you are not overclocking there is little reason to have it turned off.

The Why#

So why did FCH spread spectrum being turned on resolve the issue with my system instability? My best guess given the information I have read and certain assumptions is the following. When I moved to the new GPU, it in itself was more sensitive to EMI or the pci bus was unable to reliability lock in at the 5.0 standard due to EMI, or a combination of the both.

With FCH being turned on it was able to reduce EMI by enough of an amount to resolve theses issues.

The more you know, hopefully this helps someone else who is having the same issue.