Socket 478 / Socket 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).

Picture of Socket 478

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.

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

mPGA478B (socket 478) package - bottom view

478-pin micro FC-PGA (does not contain integrated heatspreader)
478-pin micro FC-PGA2 (with integrated heatspreader)
478-pin micro FC-PGA4 (with integrated heatspreader)

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 for your computer you will need to know your system brand and model for branded computers like Dell, HP, Gateway, etc, or make and model of motherboard in your computer.

  • If you have branded system then search first on manufacturer's website, and then on internet for "<brand> <model> CPU upgrade" or "<brand> <model> processor upgrade" (without quotes). For example, if you have Dell Dimension 4700 then search for:

    Dell Dimension 4700 CPU upgrade

  • If you can't locate information on your branded computer, or if you have a generic or a custom built computer, determine make and model of your motherboard, and then search for it. Information on retail motherboards is usually available on manufacturer's websites, and may be available on Information on OEM motherboards (motherboards used in branded computers) is usually scarce, so be prepared to read numerous forum threads all over the net.
  • If you can't find processor upgrade information for your system or motherboard then try to e-mail your system or motherboard manufacturer. Don't keep your hopes high as more often than not they do not provide upgrade information.
  • If, at this point, you still can't find what CPUs are compatible with your system, then your only option is to guess what processors may be supported by your socket 478 motherboard. Proceed only if you're willing to take a risk, because the processor you will buy may not work in your board. To see what processors your motherboard or system may support use CPU-Z or similar program to determine motherboard chipset, and then search for chipset name. You may not always find a list of CPUs compatible with the chipset, but you will likely find what Front Side Bus frequencies are supported, and what processors are supported by other motherboards with the same chipset. This should give you an idea of what to upgrade to.
  • If you still don't know what processors are supported by your motherboard or computer then here some rules, based on your current CPU, that will tell you what processors may be compatible with your computer. The first two columns should match core name and FSB of your processor, and the third column shows the fastest compatible processor:

    CPU CoreFSB (MHz)Fastest CPU
    Northwood400Pentium 4 2.6 GHz / 400FSB / Northwood
    Pentium 4 2.8 GHz / 400FSB / Northwood (difficult to find)
    Pentium 4 3 GHz / 400FSB / Northwood (impossible to find / may not work)
    Northwood533Pentium 4 3.06 GHz / 533FSB / Northwood
    Northwood800Pentium 4 3.4 GHz / 800FSB / Northwood
    Prescott533Pentium 4 2.8 GHz / 533FSB / Prescott
    Prescott800Pentium 4 3.4 GHz / 800FSB / Prescott
    Willamette400Pentium 4 2 GHz / 400FSB / Willamette

    Please note that, while these rules are valid in many cases, they do not guarantee that your socket 478 motherboard will support recommended processors. Upgrade at your own risk.

For upgrade information for ASUS, DFI, ECS, Gigabyte Technology, Jetway, MSI, PC Chips and a few other motherboard brands of 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.


2010-03-06 07:34:34
Posted by: Chris England

"Extreme" is misspelled on this page.


I love your website!


Response: I corrected the family name. Thank you!

what package?

2010-06-03 18:32:32
Posted by: interested party

this page says the Celeron D has a "micro FC-PGA4 package", but the linked page says it is a FC-PGA2 ?!

Response: Socket 478 page was incorrect. This is fixed now. Thank you!
Last modified: 10 Mar 2014
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