hi, due to spec G55 support 1600Mhz, if put 1866Mhz or 2133Mhz RAM to laptop, i guess it would be run 1600Mhz.

In the case of the Kingston HyperX PNP sticks, it is well documented on these forums that the older G74 series indeed runs it at 1600 or 1866 (depending on whatever speeds you put in...), but only two sticks at a time. I.e. putting in 2x4GB=8GB of 1866 sticks caused the IMC to overclock to 1866 MHz. However, putting in 4x4GB=16GB sticks caused the G74 to *downclock* to1333MHz, despite the rated speed of the sticks being much higher. Apparently the G73 did not have this problem: 4 sticks of 1866 would indeed overclock the IMC to 1866 properly.

These are just observations from users, and ASUS has never answered (many, many) questions as to why the G74 does this (we have guessed it is an overheat protection of some sort, since 4 higher frequency sticks may draw too many watts from the IMC). As to whether that means the G55 will behave this way with two or even four very high speed 2133 MHz sticks: it may work, it may not. Just be aware that ASUS builds in protections/behaviours into the BIOS that are undocumented, and they are not going to be forthcoming in helping you find out why PNP RAM doesn't work the way it should.

http://rog.asus.com/forum/showthread.php?26059-G55-and-PC3-1700/page2 2133
4+4 = 1866\2133
4+4+4+4 = 1333\1600

I figured that 😕 i guess i'll have to wait until 8gig 1866mhz ram sticks come out for laptops unless someone prooves me otherwize that 4 sticks of 1866mhz or 2133mhz ram will work on a G55

good , i hope thats not the case I would like my expensive gamming laptop go beyond normal laptop specs

Ok if i can't use 1866mhz ram Is it better if I use four 4gig 1600mhz ram running at CL9? or two 8gig 1600mhz sticks running at CL10? My laptop is running at CL11 atm so either way it's an improvement.