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Question MSI B450M Mortar Max M2_2 slot with NVMe SSD intermittently working...

Jun 8, 2020
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G'day all...

I've recently put together a new PC and having issues with the second M2_2 slot only intermittently detecting an NVMe drive that's installed in it.

System specs:
Mobo: MSI B450M Mortar Max - updated to latest v27 BIOS
CPU: Ryzen 5 3600X with CM 212 cooler
RAM: 32GB Corsair LPX 3200 (2x16)
GPU: MSI Ventus RTX2080S
PSU: Corsair CX550M (edited - not a 650 as originally posted)
SSD 1: WD SN750 NVMe 500GB (in M2_1 slot - Boot drive)
SSD 2: WD Blue NVMe 1TB (in M2_2)
Fans: 5 x 120mm and 1 x 140mm Deepcool RGB fans

I find I have to restart the thing a few times in order to get the M2_2 drive to appear - I usually go straight into BIOS first to check if it's detected before letting it load into Windows each time. Once it's detected it works fine and haven't had any reliability issues with it within Windows. I have some stuff installed to it and runs fine, if I restart 9/10 times it boots into Win10 and works fine - only been a few occasions it hasn't worked when restarting. It's just the initial detection of it at first startup for the day.

I have searched through various settings in the BIOS but no settings seem directly related to the M.2 drives.

Last night I swapped the two drives around, put the 500GB SN750 in M2_2 and the WD Blue 1TB into M2_1 and same thing, on first boot up the drive in M2_2 wasn't detected in BIOS, made no changes and restarted and went back into BIOS and it was there. So that tells me it's not the drive being flaky but the M2_2 slot.

I have been reading up on PCIe lanes and what not and understand the limitations with this chipset/zen2 pairing. On other posts/forums I have read there could potentially be some BIOS limitations with some being told to wait out for a BIOS update... Just odd how after a restart or two it starts working fine.

I thought I'd reach out and see if anyone else has had a similar issue and whether there's a solution.

Cheers
Carl
 
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Jun 8, 2020
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Just had an afterthought... This build has been a progressive one over a few weeks. The initial build had 2 x SATA SSD's (250GB & 1TB), GTX1070 GPU and only 4 120mm/1 140mm non LED fans. Then a couple weeks later I figured blow it and brought the 2 x M.2 drives, 2080S and LED fans. So now it's got me thinking the 550W PSU is pushing it to deliver the required watts and the M2_2 at the bottom of the mobo is first casualty of not having enough juice on initial power up... I presume on first power up, when everything spins up the initial power draw would be quite substantial. but after restarting there's most likely some residual power still in the caps and what not to lesson the load when it restarts again.

My initial calculations with the wattage use with the GTX1070 recommended a 550W PSU but with the extra load of the LED fans and RTX2080S the power usage, on average on all the various online calculators I've tried is now between 530W and 557W with recommendation for a 750W PSU.

So I have just put in an order for a NZXT 850W PSU so hopefully that rocks up by the end of the week and I'll see if my theory is correct.
 
Jun 8, 2020
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The 850W PSU arrived today and I installed it this evening, unfortunately it didn't make any difference. It still took a few restarts to get the BIOS to detect the second M.2 drive. Back the drawing board.
 
Jun 8, 2020
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Could just be a faulty drive not working properly.
Thanks for the response. I did try swapping the two drives around to check if it was the drive itself. The other drive also didn't work in the second (M2_2) slot... So that tells me somethings up with the slot itself rather than the drive.

Quite possibly just a dud mobo perhaps... Which is a pity, everything else seems to be working fine on it. Just a case if I could be bothered going through the RMA process and be without it for a month or two... and worse yet, have them not able to replicate the issue and be slogged with the vendors testing fees plus postage costs to and from - which would come to around half the cost of the board!
 

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