imac 21.5 late 2015 ram upgrade

If you really want to feel the speed and improve your imac performance.

Buy a 130$ Samsung T3 usb 256 GB SSD.

Install High Sierra to SSD

Use internal HDD to store user folders

It's smoking fast! I have this model and the SSD is so small and quiet you won't even notice it.

If you need to work with big video files:

-> save file in your desktop work from there.

When you're done move it to hdd again.

If you don't know how to do this; (pretty simple)

Grab carbon copy for example and make a bootable backup to SSD

Then visit this link and select SSD to be bootable disk:

How to choose a startup disk on your Mac - Apple Support

Next you have to go to users and there you point your home directory to your internal hd.

Or if you prefer:

Restart your Mac and depress option+command+R to acess internet recovery and install high sierra to SSD.

This way you won't loose internal hd data and you have a fresh clean high sierra install.

Later you can remove your system files from internal hd.

In this case I would recommend making a backup of the files you need to keep or just copy them to a pendrive for example and then format entire internal hdd in apfs file system.

Because if you delete system files manually you mess time machine and trash.

Hope it helps!

you can't

http://eu.crucial.com/eur/en/compatible-upgrade-for/Apple/imac-%28retina-4k%2C-2 1*5-inch%2C-late-2015%29-imac16%2C2

You don't.

21 inch screen iMac are glued up, sealed up, non-user upgradeable computing "appliances", now.

There is NOTHING inside of a 21 inch screen iMac that can be replaced by the user.

Everything is soldered into/onto the smaller screen size iMac's logic board, now.

If this is a brand new 21 inch screen iMac, you have 14 days to return it for a full refund and you can re-order/repurchase a new iMac with the specs you need.

If you have had this iMac longer than 14 days, then you would need to sell this iMac yourself and use the monetary proceeds to purchase another new 21 inch screen iMac.

FYI,

If you are wanting to speed up this iMac by having more RAM, this will give you the ability to have more room to run more apps and to process a lot more temp data related to RAM, but won't, neccessarily, make a new 21 inch screen iMac work and perform faster.

To get the fastest 21 inch screen iMac possible, you would need to spend the money to get a faster i5 or i7 CPU, AND forget a straight up standard, conventional spinning hard drive and opt either for the Fusion Drive option OR the much better option of a full SSD for getting the most speed and "future proofing" of a 21 inch screen iMac model.

The smaller screen iMacs use slower, laptop grade/style 5400 RPM hard drives (even in the Fusion drive options, as well), now which are 33% slower spinning drives than when Apple used to install the industry standard, desktop grade 7200 RPM drives into the 21 inch screen model back before 2012.

So the slower spinning hard drives may be another point of slower, overall iMac performance.

Good Luck!

Thanks. Spot on response!

Thanks my friend. Looks like a fairly easy upgrade 🙂

Please note that you can not format the internal HDD as APFS.