Error: Differential I/O input pin clkin_125 is assigned to a non differential locati

Hi thepancake,

thanks so much for your detailed reply.

I instantiated a ALT_GX block basically with its default properties.

Then I connected all its clocks to the 125MHz clock coming from outside the FPGA.

All its other pins were set as virtual, apart from the ones that generated an error if set as virtual.

In this way Quartus compiles and I am using the 125MHz for the rest of my design (where it is actually required).

The board contains two local oscillators but they are not so good, that is why I want to use an external clock.

Thanks again

AG