Heatspreader …
These Crucial memory modules are delivered without heat spreader (heatsinks), so it is necessary to keep an eye on the RAM temperature during higher overclocking with or without increased RAM voltage. Alternatively one can mount a passive or active memory coolers, which are available in different versions e.g. at our partners in About or at Amazon.
Crucial by the way grants lifelong warranty (Limited Lifetime Warranty) to the purchaser, all information about manufacturer conditions are of course without guarantee by ocinside.de.
JEDEC and XMP …
Officially the modules are designed with the JEDEC standard for 1.20 Volts DDR4 voltage to reach the CL15 timinings at DDR4-2133 easily without errors.
XMP values (Intel Extreme memory profiles) are unfortunately not available in these modules, this means there are officially only the SPD (serial presence detect) values available for the default timings. What values you can or should set exactly, you can ask here in our Forum.
Here you can see the read of SPD in the UEFI Setup of the ASRock motherboard:
Less than 4GB on booting, only 3GB in the BIOS or less than 16GB in Windows …
It can occur that the memory capacity is only indicated as approx. 3GB instead of the 16GB, because 16GB RAM or any sizes with more than 2GB have to be customized in the BIOS and/or in the OS.
Here at OCinside.de is a guide which contains among other things a table, how much RAM each OS can support. Additionally there are some topics in our forum under hints and cheat, how one can address 4GB, 8GB, 16GB or more also with 32-Bit operating systems.