The seller (ebay) is saying that my mac mustn't be compatible with 16GB can anyone tell me first hand if a 2012 A1286 can take 16GB please?
Yes. It can. You can send them to
Everymac’s specs.
But even if that info isn’t enough, my late 2011 A1278 (the same architecture of the late 2011 A1286, and this architecture was tweaked only slightly for the mid-2012 models to update to Ivy Bridge and USB 3.0) is running, as we speak, on 16GB RAM (at 1333MHz, not 1600MHz) without a hitch.
That all said, have you A) been able to run a low-level memtest on each of the RAM sticks, to verify they check out okay, and B) have you been able to given the top RAM slot a close visual inspection (to make sure there isn’t some minor debris obstructing one of the connection points which found its way there as you were pulling out your original RAM)?
SIGNIFICANT UPDATE: The pics of the two sticks of Crucial RAM you shared above are DDR3. Look at your OEM RAM sticks. Check whether they’re DDR3 or DDR3L. This is relevant if the system expects DDR3L (which runs at 1.35V) but the RAM only operates at 1.50V. Whereas throwing in DDR3L RAM into a system which came out when all RAM ran at 1.50V will work find (as the DDR3L logic will step up to 1.50V),
a system designed for DDR3L (1.35V) RAM is not designed to accept RAM which only runs at 1.50V (i.e., DDR3). It does surprise me that one stick works, but I have a sneaking suspicion that the original RAM from your MBP was/is DDR3L. If this is the case, you will need to probably return these in exchange for DDR3L, which may or may not be the same price.
The specs listed by Everymac suggest the mid-2012 runs DDR3L RAM, not DDR3.
Here’s
an additional, more technical discussion about what changed with the Ivy Bridge update. It appears 1.35V — something a DDR3L can do, but not a DDR3 — is what the system requires for RAM to function reliably (i.e., being able to use both slots without issues).
