MSI PRO B850-P WIFI Motherboard cold boots to PCIE x8 lane but fixes itself on restart to x16 lane

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msnehamukherje158702e0

DarthJarJar
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Jan 12, 2026
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As the title suggests, sometimes 4 out of 10 times, the motherboard will boot to x8 Gen 5 mode but will correct itself on restart to x16 Gen 5 mode always. I can prevent this from happening if I flip the PSU switch to 'Off' and back to 'On' before doing a cold boot, it will always boot to x16 mode. But if I shut down and keep the PSU on and start after sometime, the chances are, it will boot to x8 mode until I restart. Basically I need to kill power completely to ensure it boots to full PCIE x16 lane. Happens on latest BIOS AGESA 1.2.0.3g released on September 2025. No BIOS updates for this board after this.

PC is fully stable on either modes. No stutters, no crashes, no black screens.

What I've tried:
1. Replaced the motherboard with the shop TWICE.
2. Tried a different CPU R5 9600X, still happens
3. Replaced the GPU with an RTX 4070, still happens
4. Replaced the RAM, still happens
5. Removed my primary NVMe drive, still happens

My full specs
Ryzen 7 9800X3D
32 GB(16x2) DDR5 6000 MT/s CL 30-36-36-80
MSI GeForce RTX 5070 Gamin Trio OC White
Crucial P1 1TB M.2 Gen 3 NVMe
Samsung OLED G6 monitor

Hopefully someone can help me with this. This sounds like a BIOS issue?
 
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Svet said:
Did you put a GPU load before checking for this? Because could be a power saving mode when the GPU is idle or low usage.
Click to expand...
I did yea. It would just go from 2.5 GT/s to 32 GT/s but stay in lane X8 until I reboot PC. Quick Google search shows there are way too similar problems like mine lol, especially on MSI AM4/5 boards.
 
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I had a similar issue with AGESA 1.2.0.3g, but with a different chipset model (X670E), I opened a support ticket and they sent me a newer BIOS version that have AGESA 1.2.7.0 that seemingly solved the issue

Try opening a ticket to ask if they have one too for your motherboard model
 
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late.wall27115cd02e4 said:
I had a similar issue with AGESA 1.2.0.3g, but with a different chipset model (X670E), I opened a support ticket and they sent me a newer BIOS version that have AGESA 1.2.7.0 that seemingly solved the issue

Try opening a ticket to ask if they have one too for your motherboard model
Click to expand...
Thanks for the heads-up. I figured it was a BIOS issue as I have eliminated every possible hardware issues. I am surprised MSI is this slow on releasing newer AGESA versions for their motherboards.
 
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For me the entire AGESA 1.2.0.3 lineup has been faulty, the first BIOS version I installed had 1.2.0.3a and I experienced GPU driver hangup and BSOD, I've upgraded to one with 1.2.0.3c and I got random shutdown and chipset randomly disconnecting from the system, 1.2.0.3g was stable but messed up with PCIe lanes allocation...

More than MSI, I think AMD should change how they release AGESA updates, also because they are absolutely obfuscated towards the changes they are making into a critical component
 
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msnehamukherje158702e0 said:
As the title suggests, sometimes 4 out of 10 times, the motherboard will boot to x8 Gen 5 mode but will correct itself on restart to x16 Gen 5 mode always. I can prevent this from happening if I flip the PSU switch to 'Off' and back to 'On' before doing a cold boot, it will always boot to x16 mode. But if I shut down and keep the PSU on and start after sometime, the chances are, it will boot to x8 mode until I restart. Basically I need to kill power completely to ensure it boots to full PCIE x16 lane. Happens on latest BIOS AGESA 1.2.0.3g released on September 2025. No BIOS updates for this board after this.

PC is fully stable on either modes. No stutters, no crashes, no black screens.

What I've tried:
1. Replaced the motherboard with the shop TWICE.
2. Tried a different CPU R5 9600X, still happens
3. Replaced the GPU with an RTX 4070, still happens
4. Replaced the RAM, still happens
5. Removed my primary NVMe drive, still happens

My full specs
Ryzen 7 9800X3D
32 GB(16x2) DDR5 6000 MT/s CL 30-36-36-80
MSI GeForce RTX 5070 Gamin Trio OC White
Crucial P1 1TB M.2 Gen 3 NVMe
Samsung OLED G6 monitor

Hopefully someone can help me with this. This sounds like a BIOS issue?
Click to expand...
I have the same board, never experienced this issue.
I am on bios 7E56v2A60 and kept delaying the update since everything is working well.
Maybe try to downgrade to that version and save current settings in case you want to revert back.

PCIE page screenshot below

MSI_PCIe Subsystem S_[2026-01-13-12-22-37].jpg
 
Last edited:
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peron15a202ea said:
I have the same board, never experienced this issue.
I am on bios 7E56v2A60 and kept delaying the update since everything is working well.
Maybe try to downgrade to that version and save current settings in case you want to revert back.

PCIE page screenshot below

View attachment 208891
Click to expand...
Thanks for the suggestion. Maybe the older BIOS will indeed solve this issue but I have a 9800X3D and I don't want to fry mine as you're aware of mysterious 9800X3D deaths from older BIOS versions. I know it's mostly Asrock and Asus but there are isolated MSI cases too.
 
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