The Socket 478 is a CPU socket that utilizes the pin grid array and was used by Intel for the Pentium 4 and Celeron processors. Socket 478 was a replacement for Socket 423, which was found to be inadequate for processor speeds above 2.0 GHz. Intel released these processors in response to AMD's Socket 462 processors. Socket 478 processors ranged in speed from 1.4 GHz to 3.4 GHz. Intel eventually replaced the Socket 478 with LGA 775.
All Pentium 4 and Celeron processors in the Northwood series used Socket 478, as well as the first Prescott Pentium 4 processor and all Willamette series Celeron processors. These processors supported front-side bus speeds of 400, 533 and 800 MHz and had a physical size of 1.38-inches by 1.38-inches. Intel initially used Socket 478 for their Pentium 4 Extreme Edition processors, which had speeds of 3.2 GHz and 3.4 GHz and featured 2 MB of L3 cache on the CPU.