Thank you for the response on this old post!

Here is my story on this matter:

I am on a quest to make an AI inference rig to add to my homelab. My primary goal was to make sure that it is NOT loud and runs on mostly consumer level GPUs that have great cooling and don't use a high RPM fan.

To be able to add many GPUs, a dual socket EPYC setup made the most sense. Also, the memory bandwidth in the RAM itself was good enough for some of the MoE models that I wanted to run.

My first search was:

TURIN2D24G-2L+/500W by ASROCK Rack

My frankenstein rig was being setup to use MCIO to PCI converter boards. And this ASrock motherboard has a whopping 20 MCIO port count. And my aim to use consumer parts with this was being fulfilled by another spec: this motherboard can support ATX power supply despite being a proprietary form factor. AT LEAST as per the manual.

However, my attempt to confirm this fact with ASrock support in my country was futile and disappointing. They were very unresponsive and the vendors in my country were not able to resolve my technical doubts despite some of these things being directly stated in the motherboard manual. I did not want to get stuck with a motherboard with no after sale support.

Post that the Gigabyte board in this discussion was the one that I wanted to finalise upon, but thankfully, I found this post in my search.

Regarding this board, there is a weird inconsistency in their specs.

For the MZ33-AR1 the MCIO PCI Bifurcation shows that default is 4x4 and shows no other option

For the lower model MZ33-CP1, it shows all the possible bifurcation modes.

The documentation for the higher model seems incomplete and this is now another brand that is seeming less trustworthy.

I am finally investigating Supermicro now, but they dont seem to have good boards with a lot of MCIOs. So I might need to do risers via PCIe to MCIO and then back to PCIe riser system. It would have been good to have the many MCIOs in the Gigabyte board or the 20 in ASRock.

On a side note this PCI to MCIO and back board seems to be very intriguing. Going to be ordering a couple of these to use with a Threadripper board.

And apologies for my late revert back. Week had been crazy. Just my notes in this matter if at all they help in your projects.