I am configuring my board to use an external 25MHz crystal for the main clock. Is it absolutlely necessary to also have a 32kHz crystal on your board even if you are not using an RTC?
No. You do not need the 32k clock unless you specifically use it for some device module.
I've been using a custom dev board with only a 50 MHz high speed EXTAL for about 18 months no problem (well, no oscillator problems).
You can leave XTAL32 float, we've grounded EXTAL32 thru a 10M resistor, but I think that is just overkill for possible noise reduction, I do not believe it is required to actually do that. In fact it might be better without. I think the designer just did it so Altium would not complain it was a floating "input".
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