Crossfire not available

[Nahtan]

I've been trying to put some old parts together and put them to good use.
But I'm having trouble to get Crossfire working.

The mainboard should be crossfire compatible and I bridged the GPU's with the required cable.
Perhaps the Bios versions are incompatible?

I am using the Catalyst Control Center 19.2.2


CPU: AMD FX 8320
RAM: 6GB
GPU1: Sapphire R9 270x Toxic BIOS: 015.040.000.003.000000
GPU2: Sapphire R9 270 Dual x BIOS: 015.041.000.000.000000 
Mobo: AsRock 970 Extreme 3 2.0
 

[Nahtan]

I installed an older version of the Catalyst Control Center, Version 15.7.1.
It now displays the crossfire option, but also is showing me an error message, stating that "both bridges must be connected"
however, there are only 2 connections available for the 270x, but only one for the 270
is there any way to get around this or are they just incompatible?
from what I read, the two cards should be compatible and there should not be much performance difference, however, in unigine heaven the 270x scored 20% higher than the 270.
does that mean that I can't use one of the cards now?