Hi, I’m very interested in using the bifurcation support on the 5b to run a M.2 drive and an M.2 style 10gb nic. Has anyone been able to locate a M.2 x4 to dual M.2 x2 board / adapter?
Is this something radxa plans to release similar to their sata board for the e key slot?
I have not been able to locate one so I made one myself:
Believe me, it will be simpler to just use board that doesn’t require bifurcation to work
@semi Were you able to get these made somewhere that also soldered on the connectors or did you have to do that yourself?
We are still looking for more insights about this board, have You had chance to test some m/2 devices? how they work and is that stable enough?
What about power?
Someone asked about differential pair, is that a problem like with USB?
@jbutler You can just drop @semi file to any good PCB maker and they will produce and assembly everything for You. Jlcpcb is charing about $55 for 5x ready to use boards. Of course You can solder that Yourself and get bare boards for about $8 + shipping. The only thing that You need to pay attention is board thickness - it have to be 0.8mm.
I did order them at JLCPCB and soldered them myself. But like @Dominik already said, you can have them assembled there.
I did not test it with different M.2 devices but I had my setup running with a sata SSD and a sketchy ATX-PSU for about a month. I have openmediavault running and I have had no problems so far.
The two lanes of each differential pair should have the same lenght. Since I make a 180° turn on the board and didn’t bother with length matching I ended up with a length difference of up to 1.5mm. The difference should be less than 1ps, meaning that the length difference should be smaller than 0.1mm.
Hi, I’m very interested in using the bifurcation support on the 5b to run a M.2 drive and an M.2 style 10gb nic. Has anyone been able to locate a M.2 x4 to dual M.2 x2 board / adapter?
I think I had done exactly what you asked for 
.
The bifurcation is painful, but works with some limitations.
The power supply is insufficient if you want to use both of the slots for nvme as RAID.
My NIC was limited to PCIe Gen2 for some mystery reason, but good enough for a decent OMV usage.
Can anyone sell this M.2 bifurcation board for the Rock5B privately? Is it for sale online anywhere?
I’m looking for a way to get one too with reasonable shipping price to Serbia. So far I’ve found some stores on aliexpress but they only accept large orders.
Where You are located?
Odroid has 2x2 ($10) and 4x1 ($15) bifurcation adapters. I think those should work and fit on Rock5.
@seni shared his PCB project, so You can get it for low price on pcb manufacturer (just pay attention to cad thickness).
It low weight package, should be cheap 
@dominik Europe.
I see the Odroid 2x2 online, neat, thank you. https://www.hardkernel.com/shop/m-2-2x2-card/ M.2 2x2 Card
But, I guess it’s not a perfect fit - is @seni 's preferable?
@seni board was designed for R5B, it’s not perfect (mounting holes are about 1mm too far) but it matches everything on board. I did not tested odroid version, of course its designed for odroid boards and maybe some of those two mounting holes will collide with board elements. For sure it will stick out of board.
I do have one spare on hand… but where do you live?
Which version? Seni’s or the ODroid one? I’m interested 
One needs to be aware that none of these cards assembled according to PCIe standard.
PCIE30x2_PERSTn_M1, PCIE30x2_CLKREQn_M1 and PCIE30x2_WAKEn_M1 port1 signals are physically missing on 5B board.
PCIE30x2_PERSTn_M1 signal is exposed on RK3588 CPU’s AK26 pin which is taken by USB_HOST_PWREN_H on 5B to power USB2 and USB3 ports. Unless you are fine with side effects you can try living without it.
See RK3588 TRM for details as well as compare 5B vs 5B+/5T schematics.
Besides that second M.2 slot needs its own power circuit similar to the one powering first slot. See 24.PCIE3.0 M key X2 page here.
