How To Upgrade Ram on a 27" iMac | 2020, 2019 iMac Ram Upgrade
The 2019 27-inch iMac is still a great, powerful Mac to buy in 2020: the overall design feels dated, but it has an industry-leading 5K display and fast processors in an all-in-one. The only thing holding it back is its RAM. How do you know if you need more, how do you install it, and what’s the benefit?
I just got this refurbished iMac from the Apple Store, with a six-core i5, Radeon 580X and an insufficient 8 GB of RAM. The 27-inch iMac lets you upgrade easily through a hatch on the back.
Do you need more RAM?
Open Activity Monitor, go to the Memory tab, and look at Swap Used at the bottom. Swap is when the system runs out of real RAM and temporarily swaps memory to the disk, which is much slower; when the computer needs that memory again, it has to read it back into RAM. Over time as you open and close apps and documents, some things stay in RAM. You may have seen apps start slower if the computer’s been on a long time, or beach balls; a reboot temporarily fixes it by flushing everything out.
Test with the original 8 GB
- Geekbench: the used memory goes quite high, but swap doesn’t grow much. The memory limits what it can do. Results: 934 single-core, 3,930 multi-core.
- Premiere Pro export: a 90-second clip of my previous video (no pre-rendered files, the standard YouTube 4K preset, timed with a stopwatch). Swap usage jumped right away, relying heavily on the drive for temporary memory. It completed in 1:48, slower than real time, using well over 1.5 GB of swap.
Installing the memory
I’m adding an OWC 32 GB kit alongside the original 8 GB, for 40 GB.
- Lay the iMac on a soft, flat surface.
- Above the power connector is a small button to push in to release the memory hatch (it takes a bit of force).
- On the back of the hatch is a small diagram: push the two gray tabs toward the center and the RAM tray springs out.
- Add the memory modules alongside the factory modules.
- Push the tray back until it clicks, and replace the hatch.
Results with 40 GB
With Activity Monitor open: no swap is used at all.
- Geekbench: 994 single-core and 4,543 multi-core: a small bump on single-core and about 15% on multi-core.
- Premiere export: swap stays at 0, and the export took 1:23, versus 1:48: about a 23% improvement.
It isn’t a staggering difference on this iMac, but there are clear improvements. 40 GB may seem like a lot for users who don’t edit video or do other high-performance tasks, but you’ll see a big improvement in overall computing going from 8 to 16 GB: when the system doesn’t have to keep moving memory between RAM and the drive, you get faster app launches and fewer beach balls.
If you’re upgrading your iMac’s memory or have questions, let me know. I really believe refurbished Macs are a great way to save a lot of money: see my refurbished 16-inch MacBook Pro unboxing video.
Links
- UNLIMITED Cloud Backup for your Mac with Backblaze
- OWC 32 GB Kit (2x16GB) for 2019-2020 iMac
- OWC 16GB Ram Kit (2x8GB)for 2019-2020 iMac
- OWC 64GB Ram Kit (4x16GB) for 2019-2020iMac
- OWC 128GB Ram Kit (4x32GB) for 2019-2020 iMac
- Twelve South Backpack for iMac
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