You can use xmr-stak-cpu (or xmr-stak and configure it only use CPU).
Run it in parallel with your GPU mining software.
Don't expect to earn a huge amount on one rig though 

I have not seen any stability issues so far.

You have probably figured this out already by now, but if not... you need to disable secure boot - set to "Other OS".
To disable secure boot, you first need to disable CSM (Compatibility Support Module).

I don't have my BIOS in front of me right now, but I am sure you will find both of these by browsing around 

Have fun!

Thanks for the summary, this is useful.

Quick question: when you wrote "power all gpu and risers from vga slots", did you mean you do not run separate power to each PCI riser? Do you power the risers by connecting cables to the 3 x molex connectors on the motherboard instead?

Hello All.

I found this thread really useful while getting my rig up and running - apart from the guys that dont RTFM clogging up the thread!

In order to help people out who are looking to use both Nvidia and AMD cards, I have been trying different configurations and noting down if they work or not. Below you will see my findings so far. Hopefully this is helpful to people wishing to do the same.

Using the final (6 x 1060, 6 x 580) configuration my rig has run for about 12hrs without any issues.
Hashrates will of course depend on OC (Nvidia) OC + BIOS Mod (AMD), so I will save this info for another post.

Note that before running HiveOS, I attempted to boot to xUbuntu and Linut Mint but had lots of lock-up issues with the Xserver was starting.

Rig Specs:

Asus B250 Mining Expert
4GB RAM
Pentium i3 7100
HiveOS v0.5-32
Nvidia Asus GTX 1060 6GB Strix OC
AMD MSI Rx580 Armor 8GB OC
Risers all powered v008S

Key:

N = Nvidia Card
A = AMD Card
- = No slot (just one PCIe x 16)
x = Empty Slot

Slot Map:

A01 A02 A03
PCIEx16_A1
A04 A05 A06
B07 B08 B09
B10 B11 B12

Working configurations:

#   6 x 1060, 5 x 580

N N N
N - -
N x N
x A A
A A A

N N N
N - -
N x N
A A A
x A A

N N N
N - -
N N A
x x A
A A A

N N N
N - -
N N A
A A A
x x A

#   6 x 1060, 6 x 580

N N N
N - -
N N A
A A A
A A x