# Socket 479

Socket 479 (mPGA479M) is a CPU socket used by some Intel microprocessors. It is primarily known as the socket used by Pentium M and Celeron M mobile processors normally found in laptops, however the socket has also been used with Tualatin-M Mobile Celeron and Pentium III processors years before it. The official naming by Intel is μFCPGA and μPGA479M.

## Technical specifications

Socket 479 has 479 pin holes. Pentium M processors in PGA package have 479 pins that plug into this zero insertion force socket. Only 478 pins are electrically connected (B2 is reserved and "depopulated on the Micro-FCPGA package").
Although mechanically similar, Socket 478 has one pin fewer, making it impossible to use a Pentium M processor in a Socket 478 board. For this reason, some manufacturers like Asus have made drop-in boards (e.g. CT-479) which allow the use of Socket 479 processors in Socket 478 boards. Conversely, it is impossible to use any Socket 478 desktop Celeron and Pentium 4 processors in a Socket 479 board as they are electrically incompatible with Socket 479 despite being mechanically pin-compatible with it. For the same reason, Celeron M and Pentium M processors are pin-compatible but electrically incompatible with Pentium III-based Socket 479 boards.
Chipsets which employ this socket for the Pentium M are the Intel 855GM/GME/PM, the Intel 915GM/GMS/PM and the VIA family of chipsets such as the VN800. While the Intel 855GME chipset supports all Pentium M CPU's, the Intel 855GM chipset does not officially support 90 nm 2MB L2 cache (Dothan core) models (even though it works, it only runs at 400 MT/s FSB; some users were able to overclock the FSB to 533 MT/s on 855GM/GME/PM chipsets to support 90 nm 2MB L2 cache Dothan cores). The other difference is the 855GM chipset graphics core runs at 200 MHz while the 855GME runs at 250 MHz.
In 2006, Intel released the successor to Socket 479 with a revised pinout for its Core processor, called Socket M. Socket M supports a 667 MT/s FSB with the Intel 945PM/945GM chipsets. This socket has the placement of one pin changed from the Pentium M version of Socket 479; Socket M processors will physically fit into a Socket 479, but are electrically incompatible with most versions of Socket 479 (except using ATI north bridge RC415MD).

## Socket and naming confusion

There exist multiple electrically incompatible, but mechanically compatible processor families that are available in PGA packages using Socket 479 or variants thereof:
* Socket 478 for Pentium 4 and Celeron series desktop CPUs;
* Socket 479 for Pentium III-M (released in 2001);
* Socket 479 for Pentium M and Celeron M 3xx (this was the most common version of the socket, and was released in 2003);
* Socket M for Intel Core, Core 2 and Celeron M 4xx and 5xx processors; and
* Socket P for Core 2 processors.
Each of these above-mentioned processor families have CPU packages that are mechanically similar yet are not electrically compatible with each other, and therefore accidentally inserting them into the wrong socket configurations will not work or may result in damage to the processor and/or the motherboard. Even Intel's CPU specifications seem to be not clear enough on the distinction and instead use the package/socket designations PGA478 or PPGA478 for more than 1 of the above sockets.
Perhaps adding yet more confusion, some of the PGA-based CPUs above are also available in a BGA (or more precisely, μBGA or even μFCBGA) package which has all of the 479 contacts (balls) populated. For these CPU variants, the Intel's CPU specifications use the designations BGA479, PBGA479 or H-PBGA479. It should be however pointed out that these designations denote rather the CPU package itself and not the socket, which the BGA variants do not use at all (they are intended to be directly soldered to the mainboard, e.g. in an embedded system). The non-BGA counterparts of these CPUs use any one of the above-mentioned sockets, not just the Socket 479.