Socket M / Socket mPGA478MT
Socket M, also called mPGA478MT, was introduced at the beginning of 2006 as a socket for Core Duo and Core Solo microprocessors. A few months later, in April 2006, Intel released Celeron M 400 series family that was compatible with the Socket M. The next family that used the socket was Core 2 Duo mobile - it was introduced in August 2006. Eventually the socket was also used by Pentium Dual-core processors and by Celeron M 500 series CPUs. The socket supports single and dual-core processors with frequencies up to 2.33 GHz and Front-Side Bus frequencies up to 667 MHz. Socket M was superceded by socket P.
The socket has 478 pin holes arranged as 26 x 26 grid with 14 x 14 section removed from the center of the grid. The socket has 2 pin holes at one corner plugged. Socket dimensions are 3.6 cm x 4.4 cm or 1.42" x 1.73". Similar to socket 479, the Socket M doesn't have a lever that locks the CPU in the socket, or releases it. Instead, the socket has a special actuator that needs to be turned by about half-turn to lock or release the processor.
While the socket has 478-pin holes - the same number of pin-holes as in the socket P and the socket 478, it is not compatible with them due to different positioning of one pin-hole. Mobile Pentium III-M processors can physically fit into the socket M, but they are not electrically compatible and won't work in the socket.
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 M motherboards" section below for information on how to determine what microprocessors can be supported by your motherboard.
There are no AMD or VIA processors compatible with this socket.
Socket 479 / mPGA478M (for motherboards supporting Core Solo, Core Duo, Celeron M 400 and 500 series, Pentium Dual-Core Mobile and Core 2 Duo Mobile)
Compatible package types
478-pin micro FC-PGA
Upgrading socket M motherboards
To determine which processors are supported by your system you'll need to determine computer model (for brand-name notebooks, like Dell or HP), or a manufacturer and a model of your motherboard, and then search on manufacturer's website for that computer or motherboard model. Most manufacturers don't post CPU upgrade information for notebooks, but sometimes you may find upgrade recommendations in manufacturer's product support forums. Also try to send an e-mail to manufacturer's custom support, or post in other computer-related forums, but don't expect many responses.
Your upgrade choices are:
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