OSX will not boot with a RAM speed greater than 1400

I got 4 sticks of G Skill F3-19200C10-8GBZHD for a total size of 32GB. Rated speed is 2400Mhz.

The system will boot into BIOS at 2400Mhz, but OSX hangs during booting at any speed > 1400.
The system will also hang if XMP profile 1 or profile 2 are selected.


Board is a GA-Z87-HD3. CPU is 4790K, not currently overclocked.

The system will hang on booting with this message:
AppleKeyStore starting (BUILT: Sep 19 2013 22:20:34)


I don't have any other OS's available to test with. Is it possible this is a software problem? I've been surprised before.

1400 is kind of a sad speed to reach considering it's rated for 2400, and considering the price

I have a different system than you do, but have you tested the ram using memtest? Created a self-booting drive and run it overnight.

Maybe you need to give the ram more volts, or looser timings. Most tests show that after hitting 1600 there isn't much increase in performance outside of synthetic benchmarks (and not much there either).

My RAM is the weak point in my system from a OC standpoint. The chip will run 4.2Ghz @ 1.28v (reported in OS) on all cores all day pretty cool (65C Intel Burn Test; 55 doing video work), but I have a hard time getting my RAM to 1333 even. And it's rated at 1.65v, 9-9-9, 1600. That said, I have all the slots populated.

Strange, I am hitting 2133MHz on a 1600MHz RAM here. My RAM is so bad it doesn't even have XMP Profiles so maybe OS X does not play that well with XMP profiles? Can you try to disable it and simply use memory multiplier and auto timings instead?

tuan2195 said:

Strange, I am hitting 2133MHz on a 1600MHz RAM here. My RAM is so bad it doesn't even have XMP Profiles so maybe OS X does not play that well with XMP profiles? Can you try to disable it and simply use memory multiplier and auto timings instead?

Click to expand...

It all depends on the quality of the RAM and the luck in the silicon draw. There are so many variables involved. Some 1600mhz rated ram is actually the same stuff that's sold as 2133 mhz stuff... just sold cheaper. Few people who intend to hit 2000+ are going to risk buying 1600mhz ram and hoping it will work.

Likewise, if you have 6 slots populated (like I do) you might have a harder time getting the rated speed from your memory than if you had 1, 2, or 3 slots populated. Or, if you have 2x2GB DIMMS, it might be easier than 6 x 8GB DIMMS. Beyond that, most CPUs have the memory controller integrated in the chip. So maybe one CPU can't handle #Dimms, speed, etc, whereas another (even the same CPU, but a lucky silicon lottery winner) can. Same regarding MoBo. Same regarding voltages. Same with various bus speeds and multiplier combos.

As a side note, I recently tested my RAM at 1600mhz and it worked fine. The main change? This is the third CPU I've put in an otherwise unchanged system! (i7-950 to hex Xeon L5639 to hex Xeon X5650... the Xeons have a much, much better IMC!)