Main of Intel:

In 2006, Intel announced a plan to return the Pentium brand from retirement to the market, as a moniker of low-cost Core architecture processors based on single-core Conroe-L, but with 1 MB cache. The numbers for those planned Pentiums were similar to the numbers of the latter Pentium Dual-Core CPUs, but with the first digit "1", instead of "2", suggesting their single-core functionality. Apparently[weasel words], a single-core Conroe-L with 1 MB cache was not strong enough to distinguish the planned Pentiums from other planned Celerons, so it was replaced by dual-core CPUs, bringing the "Dual-Core" add-on to the "Pentium" moniker. This was the main purpose of this.