Yes, there is such a thing.
But unless you really need to have more than the recommended amount by Apple, I don’t recommend it. Apple states that only 32GB is the maximum ram you can install in the new late 2015 iMacs,
But , as usual some other vendors beg to differ with this ‘official’ amount and sell more than the recommended maximum. Some times it’s because that at the time of release the Apple stated maximum amount was that amount but now there’s bigger memory modules available.
Other times, the memory vendors just tested bigger chips to see just how much ram you can actually install in an Apple computer and this is the case here. OWC is the first to sell 64GB ram kits for the 27 inch retina iMacs.
The problem – and this applies especially when the computer takes a newer and faster speed of memory than previous models is that big memory upgrade are expensive.
How expensive? If you take a look at the memory price chart I have linked to at the top of the article you will see that you can fill your iMac with 32GB of RAM for under $300.00.
But, if you want to double that amount and go whole hog at 64GB then (at the time I write this), the price jumps to over $1000. That’s close to a 4x price increase for a 2x ram upgrade.
Consider also that you can buy a new 27inch iMac for $1799, and yet the ram upgrade is $1299.00, this seems a little silly to put so much money into a computer that’s not worth much more than the ram upgrade designed for it.
Now, over time the big 64GB prices will fall. When other iMacs were released with new memory requirements, the maximum amounts were priced out of this world like the 64GB are now. But they dropped in price and now a ram upgrade that used to cost over $1000 can now be had for about $100 so if you can wait, you can save a lot of money on ram upgrades for the bigger chips for any Apple Computer.
If you can wait, I would skip the 64GB, and max out the iMac at 32GB and pocket the $1000 or so difference in price.