ok, so moving down the board file, the de10_nano one
```
        Resource("clk50", 0, Pins("V11", dir="i"),
                 Clock(50e6), Attrs(io_standard="3.3-V LVTTL")),
        Resource("clk50", 1, Pins("Y13", dir="i"),
                 Clock(50e6), Attrs(io_standard="3.3-V LVTTL")),
        Resource("clk50", 2, Pins("E11", dir="i"),
                 Clock(50e6), Attrs(io_standard="3.3-V LVTTL")),
```
Why are there three Resources for clk50?