MacBook Pro 2012 i7 2.9ghz memory

Hello! I just bought a used MacBook Pro 2012 i7 2.9ghz laptop. I got it used from a computer shop on Ebay. It's in BEAUTIFUL condition and I got a good deal on it, except...

The system will ONLY take 1333mhz memory modules! Now before you jump to conclusions, I have been a computer tech for over 30 years and have owned MacBook Pros since 2007, so I know how to check out the system and look for the right memory and identify the memory size and clock speed (I'll attach some screenshots). First thing I did out of the box after it arrived was boot it. It booted with NO problems, and got on the Wi-Fi, signed in to iCloud, all the basics, and other than acting slow it worked perfectly. I expected it to act slow because it was refurbished and only came with 2GB of RAM. I had already purchased 16GB of brand new 1600GHZ PC3-12800 ram from MediaZone on Ebay, and had already checked and double checked in several online resources including Apple Support that this is the correct memory for this unit.

When I first opened the case up, (I also replaced the battery because it was listed as Battery Needs Servicing... the memory and battery were the source of the good price I got), I removed the RAM, expecting to see a single 2GB RAM Module, but was surprised when I found that there were two modules each of 2GB. I had already checked the System Profiler before I started and confirmed that only 2GB were registered on the system. I just assumed when I saw the two modules that it had had the stock 4GB originally, and one of the modules was bad, and for whatever reason this didn't get directly checked out. But after further testing things got VERY weird.

I replaced the memory with my brand new 8GB PC3-12800 1600Mhz modules, happily turned on the unit, and had my heart sink when I heard the familiar "three beeps / pause / three beeps". I said, "It's okay... probably just not cleanly set, maybe a little tarnish on the contacts in the slots..." So I re-seated them, and same thing. I swapped them in the slots, same thing. I tried one alone, then the other, same thing. So as I sat there thinking I had SOMEHOW bought 2 brand new faulty memory modules from a solid seller on Ebay (both of the companies I purchased from had 97%+ positive ratings and several thousand sales). Since this seemed very unlikely I thought, maybe they sent the wrong memory on accident. I had the old modules on the desk next to the new ones, and to my surprise the new ones did indeed have PC-3 12800 8GB printed on them, but the old modules had PC-3 10600 2GB printed on them!!! But my memory told me that the 12800's were the right ones. I spent two weeks deciding on which unit I was gonna buy, and I was dead certain that the mid 2012 MBP took 1600ghz modules. So I put the old ones back in, doing the little "slide in and out a few times to clean the contacts a bit" since one had not been working, and the computer booted right up. I opened the System Info, and it still read 2GB, but it DID INDEED say 1333Mhz next to the memory.

So I went online and began the search, first confirming everything about this model being a Mid-2012 i7 2.9GHz 1600MHz unit, including the serial # and model identifier (MacBookPro 9,2). I checked online for the specs again, confirming that it should use 1600MHz memory -- I looked at the USB specs (3.0) as well as the Bluetooth specs (4.0)...

As you can see, EVERYTHING checks out as being the unit advertised. I was just boggled. My first thoughts now were that SOMEHOW the Logic Board had been manually set to only accept 1333MHz modules, but I didn't think that was possible. I thought that possibly an incorrect firmware had been installed, but I didn't much think THAT was possible either. I pondered that, because this was a refurbished unit, MAYBE some clock IC on the Logic Board had been replaced with a clock IC from a 2011, which I found mostly unbelievable. Memories from my old PC days actually got me looking all over the board for a "jumper" LOL! I scoured the Internet and Apple Support forums as well as others, and aside from people asking about TRYING to use 1333MHz modules in this model, or use 1600GHz modules in pre-2012 models, I couldn't find ANYone writing about this problem. I'm still at a loss.

Anyone at Apple or the Community who might have a clue about this, I would really like to know. I forgot to mention that I tested the original 2GB modules by swapping them and using them singularly, and determined that both modules are good, but Memory Slot 0 is not working. So regardless of this mystery problem I contacted the seller today and they very easily agreed to a refund on them. The purchase was covered by a full warranty period anyway. I even asked if they would replace the Logic Board for me, I'd keep the same unit, because it is in nearly new condition. But they don't do that at their shop. So I'm in the midst of returning it, sadly, and finding a new one. I'm just VERY curious if anyone has any explanation for this. I'd really appreciate it!

Thank you all for indulging my very long post LOL! And I wish everyone Happy Holidays!

Thanks Again,

Michael