DDR3 compatibility

The gap between the slowest speed RAM and the fastest, is likely

too great for the fast memory to function in the slower speed Mac.

Some users of 1333MHz RAM were able to put 1600MHz RAM in

and have them work OK, but not faster than the slower RAM spec.

To assume the pin-count is the same, and voltage ranges, too.

So as was already stated, you are the spinning wheel:

And it is a gamble 😐

charlynmars wrote:

I recently upgraded the RAM in my mid-2012 MPB from 4Gb to 8Gb (DDR3-1600).

I also have an early-2009 Mac Mini that has 2Gb RAM (DDR3-1066).

Will the early-2009 Mac Mini run properly if I replace the RAM with the leftover 4Gb RAM (DDR3-1600) from the MBP?

It is usually a crapshoot. There are three things that can happen:

1. Work without issue

2. Work but create all manor of odd behavior, system crashes, etc.

3. won't boot at all.

As Macs are typically really fussy about RAM, you are spinning the wheel and

one of the three results will happen.

I can/have used the 1866 memory from my 2013 Mac Pro in my 2009 Mac Pro which uses 1066 memory.

Since the Mac Mini and MacBook Pro of certain vintage are in the discussion as first posted

those are what my general assessment is based; and reading other community discussions

where users tried several kinds of RAM, some unofficially supported & others unsupported...

As my Mac Mini (Late 2012 i7 quad server) can use the 1600GHz spec RAM similar to the

MacBook Pro of certain model build years that overlap those specs of both Mini & MB/Pro

this is where my interest in knowing the correct RAM as written in specifications. In some

locations online, there are subtle differences in those specifications in voltage & other detail

so I had read of those in an attempt to determine which varieties of marginal spec RAM may

have been problems for certain users who had issues. And these were of main brand quality.

Even OWC and Crucial offers similar spec RAM and suggests certain models can or cannot

use them, on one page; then later on in their own database, a conflict of information is found.

So while some MacBook Pro or Mac Mini (before-soldered memory) models could use slower

or faster than officially endorsed specification part not directly intended for their specific unit,

I would not recommend those with an extra part collecting dust in a drawer, to make it fit...

Every so often, especially when I used to have a hobby room with more than 78+ Macs in it,

I'd clear out or find a new home for old parts that I decided to not keep around anymore. So if

someone has extra parts and they aren't certain of their viability, I suggest learn before using.

But that's just me.

I can always afford to do without and avoid buyer remorse, twice.😝