All Pentium D processors supported Intel 64 (formerly EM64T), XD Bit, and were manufactured for the LGA 775 form factor.
The only motherboards guaranteed to work with the Pentium D (and Extreme Edition) branded CPUs were those based on the 945-, 955-, 965- and 975-series Intel chipsets, as well as the nForce 4 SLI Intel Edition and ATI Radeon Xpress. The Pentium D 820 did not work with the nForce 4 SLI Intel Edition chipset due to some power design issues, though they were rectified in the X16 version. The 915- and 925-series chipsets did not work at all with the Smithfields, as they did not support more than one core (to prevent motherboard manufacturers from using them for Xeon branded motherboards, as had happened with the 875P...