Wikipedia
Yorkfield is the code name for some Intel processors sold as Core 2 Quad and Xeon. In Intel's Tick-Tock cycle, the 2007/2008 "Tick" was Penryn microarchitecture, the shrink of the Core microarchitecture to 45 nanometers as CPUID model 23, replacing Kentsfield, the previous model.
Like its predecessor, Yorkfield multi-chip modules come in two sizes. The smaller version is equipped with 6MB L2 cache, and is commonly called Yorkfield-6M. The larger version is equipped with 12 MB L2 cache.
The mobile version of Yorkfield is Penryn-QC and the dual-socket server version is Harpertown. The MP server Dunnington chip is a more distant relative based on a different chip but using the same 45 nm Core microarchitecture. The Wolfdale desktop processor is a dual-core version of Yorkfield.
The successor to Yorkfield is Nehalem based Lynnfield.