they both share the Intel 64 64-bit technology, but the Pentium D does not include Hyper-Threading. The Pentium D's two execution cores provide two completely parallel processing streams.

Intel's top Pentium chip ... All Pentium 4 chips are single core, while dual-core Pentium models such as Pentium D and Pentium Processor Extreme Editions omit the "4" designation.

The most recent Atom used in laptops is from 2016 and it was hardly fast back then. Up until recently, there were separate brands for Celeron and Pentium processors. Intel has now bundled both of them ...