Unlike recent chipset launches from Intel, the P55 Express chipset is not backwards compatible with socket 775 Core 2 Duo/Quad/Pentium D/4/Extreme processors. New architecture calls for a new CPU socket, the socket LGA1156 - land grid array, 1156-pins.

This is the new socket 1156 on the ASUS P7P55D-Deluxe motherboard. According to Intel, the new socket uses 25% less metal than the LGA775 package.

Like LGA775 processors, the LGA1156 Core i5 chips are pinless.

The LGA1156 socket is slightly longer than LGA775 so there won't be an issues with mistakenly installing an older CPU into it. It's also not going to be compatible with any socket 775 heatsink you might have. The four holes around the CPU socket are spaced a little bit differently so they don't line up with socket 775 mounting brackets.

Unfortunately Intel has mandated that socket LGA775, LGA1156 and LGA1366 heatsink mounting holes are all going to be spaced a bit different (72mm, 75mm and 80mm on center respectively). The same injection molded plastic Intel C33389 reference fastener is used on all three thermal solution systems, so I can't say we understand why Intel didn't just pick a standard new size, say 80mm, and stick with that for Core i5 and Core i3 processors.

Next, the P55 Chipset one the ASUS P7P55D-Deluxe motherboard...