Expansion slots and 10Gbit networking options (including WiFi slot!)

Normally building a system based on a Micro-ITX board limits your available IO options heavily. You are basically dependent on whatever comes on the motherboard + 1 PCIe x16 slot.

While the same holds true for the system we are building, using some smart modern trickery we can actually get quite a lot of IO and more importantly PCIe lanes out of it!

Let’s explore that a bit and see what our options are, but with this method you’ll be able to get multiple unrestricted 10Gbit ports + NVMe SSDs and SATA drives without a problem!

10Gbps NIC vs 10Gbe

You see both terms often, why is that? Well to simplify it:

• 10Gbps NIC
  • Can be copper but can also use another medium through an SFP+ slot such as fiber or a DAC cable
• 10Gbe NIC
  • Refers to a 10Gbit copper port

PCIe lanes and Gen3/4 to the rescue

In total for the build we are doing we will have the following PCIe lanes available through various M.2 slots:

• Motherboard
  • 2x M.2 Gen4 x4 slots
  • 1x A+E key Gen4 x1 slot
    • This is the WiFi slot, I have verified that it’s a true Gen4 x1 slot on this motherboard
• PCIe Gen4 x16 slot
  • BiFurcation card with x4x4x4x4 BiFurcation
    • 4x M.2 Gen4 x4 slots

Counting the total amount of lanes that’s 6x M.2 Gen4 x4 slots + 1x A+E Gen4 x1 slot = 25 Gen4 PCIe lanes we have access to.

The platform actually has 28 PCIe Gen4 lanes in total but the “missing” lanes are likely split out to the onboard USB slots, Graphics and for instance the onboard 2.5Gbe Realtek network card.

Looking at the above configuration carefully it actually means we have access to basically all lanes that a modern desktop platform has available and that on a Mini-ITX motherboard, quite unique!

The biggest caveat is that you need to use M.2 cards as expansion cards vs normal PCIe cards but a lot of expansion cards are now available in M.2 form factor and if not you can always use a M.2 to PCIe riser card which means it isn’t really much of a limitation anymore now a days.

Later in this article I show you examples of how you can have up to 6x 10Gpbs if you wanted for instance!

Gen 4, don’t you mean Gen 5?

As of writing (2024-12) I have waited 2 months on the BD790i SE and it was still not delivered. After mailing minisforum they are having supplier issues and the production of the BD790i SE is currently suspended without a known resume data. Because of this reason I have opted to use 3x BD790i full instead of the SE version. It doesn’t really change much except that it’s a bit more expensive.

The Minisforum BD790i motherboard comes in 2 flavors, the normal and the SE version. There are 4 main differences:

1. The SE has the 7940HX CPU vs the 7945HX of the normal one
   1. Both have 16 cores, the 7945HX boosts 200Mhz higher
2. The SE has Gen4 lanes on most parts of the motherboard vs Gen5 on the normal one
3. The SE has no included heatsinks + fan for the 2x M.2 slots (and they are Gen4 instead of Gen5)
4. The SE does not come with a WiFi card installed

The price difference between the 2 at the time of writing is substantial:

• BD790i is 549 euro
• BD790i se is 399 euro

That means there is a price difference of 150 euro which is quite a lot. Looking at the difference in specifications it’s very hard to justify spending 150 extra for the difference in features.  The biggest difference is the Gen4 vs Gen5 lanes but in reality there is basically no sensible hardware that currently uses Gen5 lanes. You could argue NVMe drives can use it yes, but then you need drives that are easily twice as expensive without giving you a tangible speed difference so that isn’t worth it in my opinion.

10Gbit NIC, multiple options

Option 1. M.2 10Gbe NICs

The by far easiest option is to use one of these M.2 AQC113 10Gbe NICs and slot those in the PCIe x16 bifurcation card. There have been AQC107 versions of this NIC before this and I have also tested that one but I got the best results with the AQC113 version.

Using these add-in cards you can easily add potentially up to 4x 10Gbe NICs. But with a bit of puzzling you could even add many more if you really wanted to, read on below for extra options!

Option 2. (Ab)using the WiFi card slot

The BD790i SE doesn’t come with a WiFi card but it does have the slot on the motherboard. This is actually an advantage since we then don’t have to remove it so that it doesn’t use any power if we aren’t going to use it anyway.

But it gets better, with the appropriate A+E key Gen4 x1 riser cable and correct AQC113 PCIe NIC card you can create a full bandwidth 10Gbe port without having to use a M.2 slot for it! This is a dedicated free PCIe Gen4 x1 lane that is not used for anything otherwise. PCIe Gen4 x1 is also plenty of bandwidth (up to 16Gbps) to run a single 10Gbps NIC!

(Warning, I tested 3 versions of the AQC113 PCIe 10Gbe add-in card and only 1 of those worked at Gen4 x1 speeds which is needed to have enough bandwidth. Please buy this version (select the Macintosh compatible version))

I have tested this exact combo and with an iperf3 bidirectional test and I was able to achieve 15Gbit of total traffic, at that point you hit the limit of the PCIe Gen x1. But hey, that’s well over 10Gbit so that basically means you have a fully functional 10Gbe NIC without needing to sacrifice an M.2 slot for it.

Downside is that you do have to kind of mod it into the case but the steps for that are quite simple! I’ll show that in one of the assembly articles.

Option 3. Xikestor SKN-2BT-M2

Another option would be to get a Xikestor SKN-2BT-M2, this is a modern Dual 10Gbe NIC with an additional 2x M.2 NVME slots while only using a single PCIe Gen3 x4 slot!

The way they do this is by using a PLX chip on the board which is a PCIe switcher allowing all the peripherals to use the full bandwidth of the cards connection. However if you use all of them at the same time they of course have to share the available bandwidth.

Shared bandwidth? Ieuw!

(Only when using the NVMe drives)

Well, it’s not as bad as it sounds. I initially found this card while looking for 10Gbe networking options. A dual AQC107/AQC113 is ideal for my low power ambitions vs older Enterprise hardware!

And if you use it as such, the PCIe Gen3 x4 slot gives both 10Gbe NICs enough bandwidth to not be limited. The add-in card variants often only run on PCIe Gen3 x2 anyway so it’s basically the same thing.

However if you also want to use the M.2 slots available on this card, then you run into a shared bandwidth scenario. But it would depend on your usage scenario in my opinion. I would put NVMe drives of which you expect high performance in any of the other M.2 slots this build has available and if you still need more slots, put some lower speed, archive tier NVMe drives into this card. That way you only ever get bandwidth limited if those drives happen to be accessed at the same time.

All in all a great solution, especially if you want to max out this build with 10Gbe NICs! I personally bought one to test the card and I will likely make a video about it but I will not be using it in my own build.

My chosen setup

My setup consists of using a single M.2 AQC113 NIC in the PCIe BiFurcation card + a A+E Gen4 x1 riser from the WiFi slot of a PCIe Gen4 x1 compatible AQC113 card giving me 2x 10Gbe NICs with unrestricted bandwidth. I’m able to mod the add-on card nicely into the case with minimal changes so that’s perfect!

I guess I still also have a 3rd NIC in the onboard 2.5Gbe NIC but I have no purpose for that right now.