Help: ICE_FLAGS_PREFX

This option uses the eXternal pin as a reference for the Programmable Clock

This option uses the eXternal pin as a reference for the Programmable Clock 
(MUXCLK=P) instead of the internal crystal.  It MUST be a stable 10 MHz sine 
wave present at all times as it is also used for all tuner processing.  The 
Programmable clock is a digital phase lock loop and will maintain a stable 
phase alignment with the reference clock.

Note: For most IO modules, the PREFX must be present during the card RESET.  
The A2Dr9 only needs this flag at runtime, usually on the SOURCEPIC command.   
To be safe, put this flag in the HW config file entry.

Note: When using A2Dr9 modules, the PREFX needs to be connected to the 
middle connector on the I/O module, not the mainboard.