Why my NICs work on AM4 boards but not on B75 ones?

[SpeedRacer512]

I apologize in advance for posting questions about non-recommended hardware. It's just that I'm interested in running TrueNAS Scale in old (often consumer desktop) hardware that I have available for purchase in Brazil (i.e. no secondary market for server gear whatsoever).

I have two servers running. Here are the specifications:

1. Main server:

• TrueNAS Scale 22.12.2
• MSI B550 Mag Tomahawk motherboard
• AMD Ryzen 5 4600G
• 3x 8TB Seagate IronWolf drives in 3-wide RaidZ1 (CMR this time)
• 128GB NVMe SSD - boot pool
• 256GB SATA SSD - app pool

2. Old (backup) server:

• TrueNAS Scale 23.10.2
• MSI P8Z77-V LX2 motherboard
• Intel i5-3570K
• LSI HBA 9240-8i (9211)
• 4x 4TB Seagate BarraCuda drives in 4-wide RaidZ1 (yes, they are SMR and I hate them - didn't know better)
• A bunch (7x) of older 2.5" laptop drives that I use for testing purposes
• 128GB SATA SSD - boot pool
• 256GB SATA SSD - app pool

I'm trying to use a couple of inexpensive (i.e. Chinese knock-off) NICs (against all recommendations here) on my two file servers, but they can't seem to work on the older B75/Z77 Intel platform. They work great on my AMD AM4 server, though.

Here are their product pages:

Dual-port 10GbE NIC - https://pt.aliexpress.com/item/1005006332556280.html

Single-port 2.5GbE NIC - https://pt.aliexpress.com/item/1005005929535264.html

The problem seems to be of incompatibility of PCIe versions. On the tin, it says somewhere that the NICs require a PCIe gen 2.1 x8 (10GbE) and x1 (2.5GbE) to work. To me, that means they'd work on Gen 3.0 x16 on the B75/Z77 motherboard. But they don't. Once I plug them in, no PCIe device shows up on lspci. I have an LSI HBA on that server, that simply vanishes when I plug any of the NICs in. Both work well on the PCIe 3.0 x16/x1 slots, respectively, on the B550 board. I did the same test on 3 other B75 and 3 other AM4 boards and the result is exactly the same.

Can anyone shed a light on this matter? Why those NICs don't work on the older platform? What platform would those NIC work? Would they work on X79 or X99 boards? I'm considering moving to those platforms if I can use my NICs there.

Also, is there a source where I can learn how to debug those kinds of problems with PCIe devices?

Any help is greatly appreciated.

 

[Fleshmauler]

Reading the motherboard bios it seems the top PCIE 16 slot supports PCIE 3.0 & 2.0 x16, while the bottom x16 slot supports PCIE 2.0x4. Looking at the 10gig nic it seems to only work either with x8 or x16

Could you confirm you're putting the NIC in the top slot? I guess you can manually set the PCIE speeds to gen2 in the bios in case this motherboard is having issues negotiating?

**Edit** - I think it is important to note that this is why there is recommended hardware; weird issues from things that aren't specifically designed for 24/7 operations and inexplicable compatibility problems are something you'll face with likely minimal support if any //**Edit**