Apple iMac (Retina 5K, 27-inch, 2020) upgrade guide

Updated Oct. 18, 2026 · Written from this device's verified specifications

The 27-inch Retina 5K iMac from 2020 (model A2115, EMC 3442, order numbers such as MXWT2xx/A) is one of the friendlier Macs to upgrade - and one of the most restrictive. Memory is genuinely user-upgradeable through a door on the back. Storage and the processor are not. This guide tells you what fits, the limits, and what to watch out for before you buy anything. (The 10-core build-to-order version carries the board ID iMac20,2; the 6- and 8-core models are iMac20,1. The upgrade advice below applies to all A2115 units.)

At a glance

  • RAM: four DDR4 SO-DIMM slots, up to 128GB (4 x 32GB) at 2666MT/s, user-accessible behind the rear door.
  • Storage: SSD-only and not user-upgradeable - no M.2 socket, no drive bay, no SATA. Choose capacity at purchase.
  • CPU: fixed at purchase. Apple publishes no socket type and no upgrade procedure.
  • Build-time only: 10Gb Ethernet and nano-texture glass cannot be added later.
4x 260-pin DDR4-2666 SO-DIMM slots4 × DDR4 SO-DIMM · up to 128 GB total · 2666 MT/s
4 × SO-DIMM · DDR4up to 128 GB total
Schematic of the upgradeable slots (not to scale). Check the owner's manual for their exact positions.

Lifecycle and support

No new BIOS, firmware or driver releases are planned, so a newer CPU may not be recognised.

20202021202220232024202520262027Today11 · Release · Aug. 4, 202022 · End of sale · March 8, 202233 · EOL · March 8, 2022
Filled dots: dates published by the manufacturer. Hollow dots: estimates from third-party sources.
MilestoneDate
Release
First available to buy.		 Aug. 4, 2020 Official Announced and orderable same day; manufacturer statement.
Source ↗
End of sale
No longer sold new by the manufacturer (Dell calls this 'End of Life', Lenovo 'Withdrawn').		 March 8, 2022 Estimate Delisted from Apple's online store alongside the Mac Studio / Studio Display launch. Apple publishes no end-of-sale date; corroborated by Wikipedia, EveryMac and Low End Mac. The 2021-04-20 date from refurb.me belongs to the 21.5-inch 4K iMac, not this model.
Source ↗
End of life (EOL)
The manufacturer stops developing the product: no new BIOS, firmware or driver releases.		 March 8, 2022 Estimate Reported as marketing/sales EOL on delisting. Note this is a third-party EOL label, not an Apple statement about BIOS/firmware/driver development — macOS updates for this model are still shipping (see caveat below).
Source ↗

Dates not listed haven't been published by the manufacturer or a reliable third party.

RAM: what fits and the limits

This is the upgrade the machine is built for. There are four 260-pin DDR4 SO-DIMM slots, all of them socketed (nothing is soldered) and all reachable behind the small door on the back of the iMac, next to the vents. The base machine ships with 8GB (2 x 4GB) in two slots, leaving two free.

Buying tips

  • Buy 260-pin DDR4 SO-DIMMs (PC4-21333), 1.2V, unbuffered, non-ECC and non-parity. Registers, buffers, PLLs, ECC and parity memory are explicitly unsupported - the iMac will not accept them.
  • The machine runs memory at 2666MT/s (2667MHz). 3200MT/s modules work but simply run at 2666, so don't pay extra for speed you can't use.
  • Maximum is 32GB per module and 128GB in total with 4 x 32GB. Kingston's compatibility page talks about 64GB maximums - that reflects Kingston's module catalogue at the time, not a limit of this iMac.
  • Apple recommends modules of the same capacity, speed and vendor. Matched pairs belong in slots 1+3 or 2+4 for dual-channel operation.
  • Two 32GB modules now leave two slots free for later. Four 16GB modules give the same 64GB but use every slot.
  • Buy third-party - the rear door makes this a five-minute job, and Apple charges a large premium for its own memory kits.

How to upgrade

Before you start

  • A safe outline covers every upgrade: back up your data first; shut the iMac down completely and unplug the power cord and any cables; ground yourself (touch the metal chassis or use an anti-static strap) so you don't damage the parts; open the machine; install the new part; close everything up again; then power on and check the machine sees the change.
  • For this iMac, only the memory step involves opening anything. The four SO-DIMM slots sit behind a small release door on the back of the machine next to the vents - you don't need to open the main case or touch the display. Push the modules firmly until they seat, close the door, and check the result in About This Mac, including the memory speed (mixed-size module layouts can drop the memory to 2133MHz - pairing identical modules in adjacent slots 1+2 and 3+4 held 2666MHz in real-world testing, while the usual spread arrangement of 1+3 / 2+4 dropped it).
  • For exact disassembly and torque-free handling details, use Apple's memory installation guide as your owner's manual. For anything beyond RAM - storage or CPU - consult a proper A2115 teardown manual before you even open the case, and know that Apple supports none of it.

Steps

  1. RAM installation outline
    Back up, shut down, unplug, ground yourself. Open the memory door on the back of the iMac (it releases with a latch). Fit the modules in the correct slots, matched pairs in 1+3 / 2+4. Close the door, reconnect and power up. Check About This Mac shows the full amount and the expected 2666MHz speed.
  2. Storage and CPU
    No user procedure exists. Apple publishes no upgrade steps for either, and both involve removing an adhesive-bonded display and the logic board. Use external Thunderbolt 3 storage instead, and choose the CPU at purchase.

Good to know

  • Apple doesn't publish a socket type or supported CPU list for this model - the LGA 1200 reference is inference, not documentation.
  • Apple's documents say 'SSD' but never describe a socket. Teardowns report the NAND soldered to the logic board; either way there is no standard internal upgrade path.
  • Memory speeds with mixed-size modules can drop to 2133MHz - check About This Mac after installing.
  • 10Gb Ethernet, the 8TB SSD and the nano-texture glass were build-to-order only.

Frequently asked questions

How much RAM can the iMac (Retina 5K, 27-inch, 2020) take?

128GB, using 4 x 32GB 2666MT/s SO-DIMMs. The per-module ceiling is 32GB. Kingston's page mentions 64GB configurations - that's a limit of Kingston's range at the time, not of this iMac.

What type of RAM does it use?

260-pin DDR4 SO-DIMM, PC4-21333, 1.2V, unbuffered, non-ECC, non-parity. ECC, registered/buffered and parity modules are explicitly unsupported. 3200MT/s modules work but run at 2666MT/s.

Can I upgrade the SSD in the 2020 27-inch iMac?

No. It's SSD-only with no M.2 socket, no drive bay and no SATA interface, and the NAND is tied to the T2 chip and treated as non-serviceable. Configure capacity at purchase, then expand externally via Thunderbolt 3 NVMe enclosures or network storage. The SDXC UHS-II slot is removable media, not boot storage.

Can I upgrade the CPU or the graphics card?

No. Apple publishes no socket type and no supported CPU list, and reaching the chip means a full teardown with adhesive-bonded display removal. The 10th-generation Comet Lake-S parts are in a 65W-125W desktop class that points to LGA 1200, but that's inference - treat the processor and the Radeon Pro GPU as fixed at purchase.

Do I need to open the whole case to add RAM?

No. All four slots are behind the user-accessible memory door on the back of the machine, next to the vents. Apple's memory guide has the exact procedure.

Can I add 10Gb Ethernet later?

No. 10Gb Ethernet and the nano-texture glass were build-to-order options and cannot be added afterwards. The standard model has Gigabit Ethernet and two Thunderbolt 3 ports.

Official documents and references

This guide was written with AI assistance from the compatibility data PartsPrices verified against the manufacturer's documents. Always check your exact model and the owner's manual before buying or opening your computer.