Somebody tested mainboard Asus B250 with window 10 (look at the mainboard layout for your references) and dont forget to make power as A-B-C carefully, it could recognize up to 16 GPUs P106-100 and each achieved hashrate at ~25Mh/s, total around 403 Mh/s, too good to be true!

Updated: Now we are successful on setting 21 GPUs on Asus B250, setup: Core i3-7100, 8 Gb RAM, 32 Gb Virtual Memory (for >16 GPUs, need more than 16 Gb Virtual Mem). Riser's requirement is not that much, just use the cheapest PCIE 1 to 4 extender.

This's real. My friend is visiting China for buying some devices, and this is the picture he sent me.
He also asked them how they could make this happen, they said they just update window 10 to version 1709. Btw, I think maybe this's only possible for Asus mining card P106-100 which they used.
I'm waiting him back next week, then we could have some further tests.
 

can be true
some info on internet says that it is possible with latest windows update
gotta try it and see if its true

You can actually run mix of cards above 8 in Windows 10. I have 9 gpus mining successfully (all cards). iirc the 8 gpu limit is only from a particular mfg. AMD/Nvida.

It sounds good with 25 Mh/s. When I push power limit to 100%, it could reach 26Mh/s, but I run it with 85% now for safe and stable operation, so far so good with 24.5 Mh/s.

https://imgur.com/a/Yy3bE

I ever tested 15 cards P106 on Simplemining OS, but hashrate is not impressive with 20.9 Mh/s.

https://imgur.com/a/QMdrP

I will try to test with 16 cards on win 10 ver 1709 next week as I got new purchased P106-100.