Pentium D

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 90 nm 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 two cores.

By 2004, the NetBurst processors reached a clock speed barrier at 3.8 GHz due to a thermal (and power) limit exemplified by the Presler's 130 watt thermal design power (a higher TDP requires additional cooling that can be prohibitively noisy or expensive). The future belonged to more energy efficient and slower clocked dual-core CPUs on a single die instead of two. However, the Pentium D did not offer significant upgrades in design, still resulting in relatively high power consumption.