Pentium D is a range of desktop 64-bit x86-64 processors based on the NetBurst microarchitecture, which is the dual-core variant of the Pentium 4 manufactured by Intel. Each CPU comprised two cores. The brand's first processor, codenamed Smithfield and manufactured on the 90 nm process, was released on May 25, 2005, followed by the 65 nm Presler nine months later. The core implementation on the 90 nm "Smithfield" and later 65 nm "Presler" are designed differently but are functionally the same. The 90 nm "Smithfield" contains a single die, with two adjoined but functionally separate CPU cores cut from the same wafer. The later 65 nm "Presler" utilized a multi-chip module package, where two discrete dies each containing a single core reside on the CPU substrate. Neither the 90nm "Smithfield" nor the 65 nm "Presler" were capable of direct core to core communication, relying instead on the northbridge link to send information between the 2 cores.