So I purchased some standard Crucial DDR3-1333  PC3-10600.

If you go to crucial’s website and you enter in a P55 motherboard, you will get this suggested memory:

CT2KIT25664BA1339

I ordered 2 4GB kits, each with with 2 2GB dimms.

The dimms all looked like this:

here is what CPUZ saw from the SPD of the dimm:

So, everything seemed fine until I started to get random reboots every couple days.

I tried every possible combination of the dimms, and I always got the same result; hard-reboots.

I felt the odds of all 4 dimms being faulty is roughly zero, so I decided it must be the motherboard, until I started reading these comments on newegg about my memory.  There are/was a very high percentage of people claiming the memory did not work on their P55 motherboard.

Then I started to see newegg stamp certain memory P55 Core i5/i7 compatible, which didn’t seem to make sense, because any memory that adheres to JEDEC spec for PC3-10600 should be compatible.¿?

I found Intel’s own Validation Results for DDR3-1333 on P55 here.

It lists Crucial’s CT25664BA1339, but specifically the CT25664BA1339.16FF.

Looking closer at my memory I found it to be CT25664BA1339.M16SFD.

for reference this dimm uses micron chips with markings: 9ND22 D9JNM

Crucial said the last string of this part number is for internal use only, and refers to which chip/set is being used on the dimm.  The crucial representative said it should make no difference with respect to P55 compatibility, and was perplexed why Intel would specifically approve the 16FF.  In fact as a consumer you cannot even see what the internal chipset number is before you buy online, but you can call and ask to order a specific one over the phone.

I did just that, and ordered a set of CT25664BA1339.16FF over the phone from crucial, they looked like this:

Notice the Micron label on the left?  I assume this means the dimm itself was manufactured by Micron, and resold by crucial.

(my other CT25664BA1339.M16SFD dimms don’t have a micron sticker.)

The CT25664BA1339.16FF dimm uses different micron chips marked: 9NF22 D9KPT

So the Crucial CT25664BA1339.16FF is in fact a Micron MT16JTF25664AZ-1G4F1 dimm.

CPU-Z’s information from the SPD agrees:

It is no surprise that both the Crucial CT25664BA1339.16FF and the Micron MT16JTF25664AZ-1G4F1 passed Intel’s validation tests, as they are the exact same dimm:

These new Micron dimms seem to run fine in my system without any problems.

I still don’t know why the P55 chipset/CPUs have problems with the non-16FF crucial dimms.  So I by no means really understand the root of the issue, but I thought others might find this interesting. 

The memory Crucial will send you for a P55 system may not be the memory you want. 

It also seems that many DDR3 kits that seem fine otherwise, do not work right with the P55.