Memory RAM for PC - is important the voltage value for performance and impact in the motherboard?

Question

There is the option to buy a new PC Desktop, about the memory ram, there are these two options

Memory Kingston Fury Beast, 16GB, DDR4, 3200 MHz, PC4-25600, CL16, 1.35V.
Memory Kingston Fury Beast, 16GB, DDR4, 2666 MHz, PC4-21300, CL16, 1.2V.

At a first glance the first seems better than the second due the MHz value. But being curious - the reason of this post - observe that the volts values are different too: 1.2 vs 1.35

Because I am not an expert, about the volts

Question 1:

• What is the best recommendation, the higher or lower? and why? or it does not matter?

Question 2

• What is the best recommendation for the motherboard, the higher or lower? and why? or it does not matter? My concern is that it has any negative impact in the motherboard in someway

Consider the two questions involving performance and time life concerns.

Answer 1

The best recommendation based on how you asked would be...

• If you're doing a pc where you specifically care about low power and heat, such as if it were a home theater type pc where there is no fans in the case and you wanted extreme quiet then choose the lower voltage at 1.2v because that theoretically will be using the least amount of power and generating the least amount of heat which is what would be important here versus memory speed and performance.
• but for any regular pc and one that you favor performance then get the 1.35v higher clock speed ram you mentioned.
• I can't specifically tell you how much more heat a 1.35v DDR4 dimm would be over a 1.2v dimm; if the 1.35v dimm were cheaper I would simply buy that over any 1.2v ram.

The 1.35v is within spec for DDR4 and is nothing to be worried about. The 1.2v is the original reference voltage for the DDR4 spec when it first came out however long ago. Nearly every motherboard supports 1.35v.

Best thing to do is for the motherboard make/model you're thinking about, check their QVL (qualified vendor list) and RAM compatibility before you buy RAM. You are not required to buy any specific RAM they list, use it as a reference such that if they list a bunch of 1.35v dimms at the higher clock speeds then you can be sure that mobo supports that clock speed. But, for example, if that list only shows up to DDR4-3200 and doesn't list any DDR4-4xxx, then don't go buy a DDR4-4xxx dimm.

The lower clock speed dimms all run at the reference 1.2v DDR4 voltage. All the performance ram simply runs at 1.35v in order to get that higher clock speed. There's very little to be gained or lost by trying to decide between the 1.2v or 1.35v other than theoretical power usage but that may even be a mute point since typically ram automatically downclocks itself to work with the ram speeds the motherboard is looking to use... which is to say even a DDR4-5133 may still work on a motherboard that doesn't advertise it supports it... but I'd only try that if I already had the ram in hand versus buying it and hoping it worked. A 1.35v dimm will not have any kind of negative impact.