[1] It is used in Intel Core microarchitecture and NetBurst microarchitecture (Dempsey) based DP-capable server processors, the Dual-Core Xeon is codenamed Dempsey, Woodcrest, and Wolfdale and the Quad-Core processors Clovertown, Harpertown, and Yorkfield-CL.
The word "socket" in this instance is a misnomer, as the processor interface has no pin holes.
Instead, it has 771 protruding lands which touch contact points on the underside of the microprocessor.
The "J" in "Socket J" refers to the now-canceled processor codenamed "Jayhawk", which was expected to debut alongside this interface.
Small adapters developed by Chinese computer DIY enthusiasts are available to allow LGA 771 CPUs to be installed in LGA 775 motherboards, if the BIOS microcode supports them (but it is also possible to add supporting microcode manually).