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Variation of already asked question:

I now understand that I can add two matched 8 GB sticks of RAM into the two empty slots, even though the other two slots are filled with two 4 GB modules. But is there a problem having one pair 1.5v if the other pair are 1.3v?

It would appear to not be a problem, if as reported elsewhere, the iMac has 1.5v preinstalled and Crucial is recommending 1.35v sticks. Is that a faulty assumption?

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With iMac 2012 you mean the model without an optical drive on the side? 21.5" or 27" model? – MacLemon Dec 10 '12 at 0:06
MacLemon: Late 2012 27" – Freeradical Dec 10 '12 at 13:42
You do know that Late 2012 27" are the ones that are new and thin, but I will refer it as 2013 model. Anyway, they are supposed to work anyway, but it's always better to use Apple default. – Shane Hsu Jan 18 '13 at 8:45

I wouldn't use anything but 1.5v RAM in the 27-inch iMac (Late 2012) as that's what my go-to Apple Memory site lists as compatible.

I also can't believe I'm seeing 32 GB of memory for sale for just under $260 as that just seems too cheap to be true.

If you are looking elsewhere for RAM, I would encourage you to select non-stacked chips on the SO-DIMM as we don't know how warm these devices run and the last generation of 27-inch iMac put out significant heat and had a lot more aluminum to radiate that energy before a fan and convection were needed to assist in heat dissipation.

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According to this article over at OWC all iMac late 2012 models ship with 1.35 Low Voltage RAM... – Henrik Söderlund Jan 24 '13 at 3:40

For the iMac 27" (Late 2012) model any RAM that fits the required specification can be used. The iMac (27-inch, Late 2012) has four SDRAM slots, each of which can accept a 4 GB, or 8 GB SO-DIMM. RAM Spec from Apple's tech docs: PC3-12800, (1600 MHz) DDR3, 204-pin, SO-DIMM
4 * 8GB Modules can be obtained in Europe for under 200€. (YMMV)

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