ThinSkin writes "Nearly 18 months after rival AMD released its 64-bit processors, Intel quietly added its first 64-bit Pentium 4 microprocessors to the market on Sunday. Four versions of the Intel Pentium 4 6XX series were announced at speeds up to 3.6-GHz, a frequency grade lower than the existing 5XX series. Prices will range from $224 to $605. Intel also added the 3.73-GHz Pentium 4 Extreme Edition to its lineup, a $999 chip that is fabricated on a finer 90-nm process than its older 130-nm P4EE components. As Slashdot previously reported, the 64-bit series will likely be the major enhancement to the Pentium 4 line before the introduction of the Pentium D "Smithfield," Intel's first dual-core part, which is slated for next quarter."