mauried:
The parallel resistor is normally in the PIC or AVR.
Without it , the oscillator wont run at all.
Really? I build boards all the time with ATMega328P-PU chips and use a 16 or 20Mhz crystal along with two 22pf caps and it runs fine without any parallel resistor there once I switch the chip's fuses over to external oscillator.
This has been discussed here: 1M resistor across crystal ? - General Electronics - Arduino Forum
Parallel resistor looks to be optional except for some unusual crystals, none of which I have ever run across.