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1 Rookie


2 Posts


May 26th, 2024 15:04

5820 - Core X w/ 48 lanes + NVME Flex Bays

Hi, I purchased a 5820 from dell's refurb's site with a Core 10940X. It came with a 2TB NVME in a FlexBay

I read (after the fact, my fault) that Dell states that CoreX drives can only use one NVME due to PCIE lane limitations.

I see that previous generation and lower model CoreX drives range from 28 to 44 lanes. The 10940x has 48, the same as the W Xeon processors.

The motherboard has two mini-sas connectors. Will I be able to use a 2nd NVME drive (after purchasing the parts of course)?

Or is this a Dell limitation applied to any CoreX processor regardless of their lane count?

I have a 4x NVME pcie card that should work (asus hyper v2). However, if I can save a PCIe slot I'd like to do so. My storage array is an external housing using an LSI card with external connectors.

I also realized after the race that Core X can't use ECC ram. This is a Proxmox homelab server and wanted a high core count CPU. I'd go back to the drawing board and find a Xeon variant but the price was too good that I'd like to get this one to work.


5 Practitioner


5.2K Posts

May 26th, 2024 15:45

Before taking the plunge and purchasing additional parts, look inside the empty flexbay (usually the top left) next to the current boot drive (usually the top right).  Verify if the drive connector being covered with a label.  If there is no label, you can just remove the current boot drive assembly (use a paperclip to unlock) and connect to that empty flexbay.  The test should tell you the readiness of connection setup.

Upon the system boot, it will recycle 3 times to adjust BIOS settings, that is normal.  If the system can not boot, it means that the empty flexbay can not be used as it was not wired to CPU at motherboard level.

1 Rookie


2 Posts

May 26th, 2024 19:20

@Chino de Oro​ Ahh! Thanks bud! I was thinking of swapping the drive into the bay you referenced to try it.

I had ordered the PCIe nvme adapter without realizing how the flexbays worked. Heck, I didn't even pay attention to the storage configuration. Once I realized it came with a 2TB NVME, if I can get the other flexbay to work I can add one of my existing 2TB NVME in there, mirror the drives in proxmox, and save a pcie slot.

Or - if it doesn't work then I'll convert the bay back to SATA (backplanes are cheap on ebay) and load it up with my rust storage instead. 

7 Technologist


10.6K Posts

May 27th, 2024 00:09

Besides chino’s answer, this Dell article may help

note: Installing Data Cable :

Connect the upper data cable (U.2_P1) to PCIE1 port on the motherboard, lower data cable (U.2_P0) to PCIE0 port on the motherboard.

Connector for Precision 5820 is located next to CPU


5 Practitioner


5.2K Posts

May 27th, 2024 03:38

Just want to add some suggestion.  If the top left flexbay is working, you can use a U.2 adapter to install your existing 2TB using the already included SATA bracket.  See example below.

You can convert the 5.25" bay to hot swap dock with x4 additional 2.5" SATA SSD.  See example below.

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