Mellanox ConnectX-3 on AM5 motherboards. Success stories?

[Frigodedo]

I have both a daily driver PC and an small Unraid NAS one, both using MELLANOX ConnectX-3 MCX311A-XCAT cards. As the PC's 13th gen. Intel CPU has been nothing but trouble, I intend to move to AMD's AM5 platform, but I've read about severe issues when pairing later NIC generations (ConnectX-4) with X870E boards, if they seemingly work with X670E ones (some people seem to solve similar issues by taping the SMBus pins).

Is there anyone successfully using the old MELLANOX ConnectX-3 cards on AM5 chipsets-based mainboards?

 

[Falloutboy]

O.K I have 3 X670Es what you might run afoul of though is the PCIe lines available if you are intending to use a 16x pcie video card with it.

I believe the MCX311A-XCAT requires 8 PCIE lanes , the 2nd slots on the X670E and indeed any AMD series other than Epic wont have these to spare, I believe they are 4 PCIe 3/4 lanes on the second port. If you are planning to run video off the IGD this wont be a problem as you can then use the x16 slot for CX3, there are ways around this with pcie extensions and passive splitters that can convert the x16 to 2 x 8s but that can start getting messy, more than happy to tell you about them if you want to know though.

 

[Frigodedo]

…I believe the MCX311A-XCAT requires 8 PCIE lanes , the 2nd slots on the X670E and indeed any AMD series other than Epic wont have these to spare, I believe they are 4 PCIe 3/4 lanes on the second port…

Thanks. Luckily, I'm using the single SFP+ socket version of the card, which is physically PCIe 3.0 x4 and can work with less than that. I've been checking a few mainboard offerings where the PCIe slots' type and lane count match my needs (I'm careful to read what gets halved or disabled depending on other components usage such as NVMe slots and SATA ports).

I'm more worried about possible compatibility issues at the BIOS level (such as not achieving POST) or any AMD-specific gotchas.

 

[blunden]

It doesn't make much sense that X870E and X670E would act any differently since the chipsets themselves are essentially identical apart from X870E motherboards splitting off a few CPU PCI-E lanes to the required USB 4.0 ports. The manufacturer could've made some changes to the trace layout etc. on the newer model but other than that they shouldn't be meaningfully different.

 

[Wolfcastle]

I’m running a ConnectX-3 at 40Gbps on a B650 board (specifically the Asus ProArt) without any issues.

 

[Frigodedo]

I’m running a ConnectX-3 at 40Gbps on a B650 board (specifically the Asus ProArt) without any issues.

Thank you. I'm probably going to go for either a X670E or a X870E (each has its little compromises in most motherboards, the latter not being as advantageous as it might look like due to the mandatory USB4 support eating a whole bunch of PCIe lanes. I'll probably get one of the former).

 

[blunden]

Thank you. I'm probably going to go for either a X670E or a X870E (each has its little compromises in most motherboards, the latter not being as advantageous as it might look like due to the mandatory USB4 support eating a whole bunch of PCIe lanes. I'll probably get one of the former).

Yeah, that's what I did too. USB 4.0 isn't very useful for me.

 

[Wolfcastle]

Thank you. I'm probably going to go for either a X670E or a X870E (each has its little compromises in most motherboards, the latter not being as advantageous as it might look like due to the mandatory USB4 support eating a whole bunch of PCIe lanes. I'll probably get one of the former).

I went with that board specifically because it allows me to split the PCIe as x8 across both of the PCIe x16 connectors so I am running both the GPU and the connectx card as x8.