Socket 478 (also known as mPGA478, mPGA478B) is a 478-contact CPU socket used for Intel's Pentium 4 and Celeron series CPUs.Socket 478 was launched with the Northwood core to compete with AMD's 462-pin Socket A and their Athlon XP processors. Socket 478 was intended to be the replacement for Socket 423, a Willamette-based processor socket which was on the market for only a short time. Socket 478 was phased out with the launch of LGA 775.