Socket 478 (mPGA478B)

Socket 478 (mPGA478B) is a Pin Grid Array (PGA) socket for microprocessors based on Intel NetBurst architecture. This socket was introduced in August 2001 as replacement for short-lived socket 423. The socket 478 supports desktop and mobile Pentium 4 and Celeron processors from 1.4 GHz to 3.46 GHz with effective front-side bus frequencies 400 MHz - 1066 MHz (100 MHz - 266 MHz QDR). This socket was phased out in favour of socket 775 (LGA775).

One major difference between the socket 478 and older sockets is the socket size. The distance between pin holes in socket 478 is twice smaller than the distance between pin holes in the socket 370, which was used by older Celeron, Pentium and Pentium III families, and in the socket 423 used by first generation of Pentium 4 microprocessors. This results in much smaller socket size - only 1.38" x 1.38" (3.5 cm x 3.5 cm). Another difference between socket 478 and earlier sockets is the arrangement of pins. Pentium and newer CPUs, including socket 423 Pentium 4 microprocessors, had pins arranged as two grids where one grid was diagonally shifted relative to another grid by 1/2 of the distance between pins. In mPGA478B the pins are arranged as one grid, that is the same way as in Intel 80486 and older microprocessors.

The mPGA478B has grid size 26 x 26 with a 14 x 14 section removed from the center of the grid. Two pin-holes in one corner of the socket are plugged, so there is only one way to install the CPU. The total number of pins is (26 x 26) - (14 x 14) - 2 = 478.

  Supported processors  

All processors in the table below will physically fit into the socket, but not all of them are supported by all motherboards. If you're upgrading an old computer system please make sure that the CPU is compatible with your motherboard. Please see "Upgrading socket 478 motherboards" section below for information on how to determine what microprocessors can be supported by your motherboard.

CPU Family	Frequency	The fastest CPU(s)
Celeron D (micro FC-PGA4 package)	2.13 GHz - 3.2 GHz	Celeron D 350
Celeron Northwood	1.5 GHz - 2.8 GHz	RK80532RC072128 (BX80532RC2800B)
Celeron Willamette	1.5 GHz - 2 GHz	RK80531RC041128 (BX80531P200G128)
Mobile Celeron	1.2 GHz - 2.5 GHz	RH80532NC060256
Mobile Pentium 4 processors (micro FC-PGA4 package)	2.4 GHz - 3.46 GHz	Mobile Pentium 4 552
Mobile Pentium 4-M processors (FC-PGA package)	1.4 GHz - 2.6 GHz	RH80532GC064512
Pentium 4	1.4 GHz - 3.4 GHz	RK80546PG0961M (BX80546PG3400E) RK80532PG096512 (BX80532PG3400D)
Pentium 4 Exteme Edition	3.2 GHz - 3.4 GHz	RK80532PG0962M (BX80532PG3400F)

Note: All processors are in 478-pin micro FC-PGA2 package, unless stated otherwise.

Mobile Pentium III-M and Pentium M microprocessors use different type of socket. There are no CPUs from other manufacturers compatible with socket 478.

  Compatible package types  

Please note that there are three different 478-pin packages, and only one of those packages is compatible with socket 478. The picture on the right shows the package that fits into the mPGA478B socket.

  Upgrading socket 478 motherboards  

To determine the fastest processor you can upgrade to you'll need to:

• Determine manufacturer and model of your motherboard,
• Search on manufacturer's website for the motherboard model.

For upgrade information for ASUS, DFI, ECS, Gigabyte Technology, Jetway, MSI and PC Chips motherboards please check CPU-Upgrade motherboard database.

  Processor Installation  

For processor installation instructions please look at your motherboard manual, or download installation instructions for boxed Intel Pentium 4 microprocessors from Intel website.

Important notes about Pentium 4 CPU installation:

• When you handle the processor avoid touching the pins.
• During CPU installation allow the processor to drop into the socket - do not try to force it into the socket! Pentium 4/Celeron CPUs in micro FC-PGA2 package have more delicate pins than older package types, if you try to force it you can easily bend the pins.