Summary, Clock Device Support


udcf(4)
Almost no hardware dependency (other than having USB)
Limited precision (as polling over USB is needed)
Support for MSF (.uk) is planned

nmea(4)
Works with almost all GPS receivers, serial-, USB-, CF-, and PCMCIA-attached
Highest possible precision with PPS capable devices, requires special wiring

mbg(4)
High precision
Industrial grade receivers