My MacBook Pro Mid 2010 has two DDR3 so-SIMM slots capable of hosting totally 8GiB. I already have one kingston value ram module 1066 MHz 4GiB and I want to buy another 4GiB module. There is the choice between the same module or the same but with low voltage (1.35V).

Both are up to 1600 MHz which should not be a problem because it is higher than the frequency it will run. The low voltage module sounds neat, but will the old and the new module work well together?

I guess the low voltage module will just run on the usual ram voltage, right?

  • I'd say go for the same. If Apple thought their computer would run well with low voltage RAM, I expect they would have fitted it, if only to extend battery life. Nov 23, 2014 at 17:43

1 Answer 1


In almost all cases a DIMMs will work at multiple voltages.

Some actually state that: E.g:

  • 1333MHz at 1.35v,
  • 1600MHz at 1.5v
  • List item

(Sold ofcourse as 1600MHz capable low voltage RAM).

Other might not state that but almost all (99% ?) will work when you feed them sligthly (say up to 10%-15%) more power than specced.

So yes, it will almost certainly work.

That means a 1.35v DIMM (capable of 1.35 and 1.5v) and a 1.5v only DIMM will work fine (both at 1.5v).

  • I bought the low voltage 1600 4g module. It didn't work together with my old 4gb 1066 module, my mac didn't start up. Using the new module by itself worked, so I thought I could just buy another low voltage module to have the desired 8gb ram. Having bought a second 1600hz 4g low voltage module, I see that my mac doesn't start up either. My solution: return both modules to the store, buy an old 1066hz 4g module of the excact same type like the old 4g module I already have and it works fine. I seriously don't know why it didn't work. ram is just sth very very sensitive, that's what i've learned.
    – flaudre
    Dec 1, 2014 at 16:33
  • That is weird. I used to happen with ancient PCs unless you manually set the speed to the lowest common dominator, but there days DIMMs usually come with a chip containing known working standard speeds and the BIOS/firmware/UEFI should just figure things out, set a working value and boot.
    – Hennes
    Dec 1, 2014 at 18:14

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