Apple iMac (Retina 4K, 21.5-inch, 2017) vs Apple iMac (Retina 5K, 27-inch, 2020)

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iMac (Retina 4K, 21.5-inch, 2017) compared with iMac (Retina 5K, 27-inch, 2020)

	AppleiMac (Retina 4K, 21.5-inch, 2017)	AppleiMac (Retina 5K, 27-inch, 2020)
Overview
Released
Released	June 2017	August 2020
Performance
Processor
Processor	Intel Core i5-7400, Intel Core i7-7700 or Intel Core i5-7500	Intel Core i5-10500, Intel Core i5-10600, Intel Core i9-10910 or Intel Core i7-10700K
CPU cores
CPU cores	4	6, 8 or 10
CPU threads
CPU threads	4 or 8	12, 16 or 20
Graphics
Graphics	Radeon Pro 555 (2 GB VRAM) or Radeon Pro 560 (4 GB VRAM)	Radeon Pro 5300 (4 GB GDDR6), Radeon Pro 5500 XT (8 GB GDDR6), Radeon Pro 5700 (8 GB GDDR6) or Radeon Pro 5700 XT (16 GB GDDR6)
Memory
Memory	8 GB, 16 GB or 32 GB	8 GB, 16 GB, 32 GB, 64 GB or 128 GB (better)
Storage
Storage	256 GB to 1 TB	256 GB to 8 TB (better)
CPU
CPU	3.0 GHz quad-core Core i5 with Turbo Boost up to 3.5 GHz, or 3.4 GHz quad-core Core i5 with Turbo Boost up to 3.8 GHz; both configurable to 3.6 GHz quad-core Core i7 with Turbo Boost up to 4.2 GHz	Six-core Core i5 at 3.1 GHz (Turbo Boost 4.5 GHz) or 3.3 GHz (4.8 GHz), or eight-core Core i7 at 3.8 GHz (5.0 GHz). Upper two bases configurable to 3.6 GHz ten-core Core i9 (5.0 GHz). Exact CPU identities follow Geekbench. Apple specifies a 5.0 GHz Core i7 limit in this iMac, while Intel lists 5.1 GHz for the chip itself.
GPU
GPU	Radeon Pro 555 with 2 GB VRAM in the 3.0 GHz base; Radeon Pro 560 with 4 GB VRAM in the 3.4 GHz base	Radeon Pro 5300 with 4 GB GDDR6 on the two Core i5 bases. Upper base has Radeon Pro 5500 XT with 8 GB GDDR6, optionally Radeon Pro 5700 with 8 GB or 5700 XT with 16 GB GDDR6.
Memory type
Memory type	2400 MHz DDR4; 8 GB standard, configurable to 16 GB in the lower base or 16/32 GB in the upper base. Two SO-DIMM slots require removal of the glued display and logic board to access (iFixit).	2666 MHz DDR4; 8 GB standard as two 4 GB modules. Four user-accessible SO-DIMM slots; configurable to 16/32/64/128 GB on every base.
Storage type
Storage type	Lower base: 1 TB 5400-rpm hard drive, 1 TB Fusion Drive or 256/512 GB SSD. Upper base: 1 TB Fusion Drive or 256/512 GB/1 TB SSD.	Lower base: fixed 256 GB SSD. Middle base: 512 GB/1/2 TB SSD. Upper base: 512 GB/1/2/4/8 TB SSD.
Display
Screen size
Screen size	21.5″	27″
Resolution
Resolution	4096 × 2304	5120 × 2880 (better)
Panel
Panel	IPS LCD	IPS LCD
Brightness
Brightness	500 nits	500 nits
Display type
Display type	LED-backlit Retina 4K display; IPS panel confirmed by EveryMac; Apple does not publish native refresh rate in this model’s specification sheet	LED-backlit Retina 5K display; IPS panel confirmed by EveryMac. Apple does not publish native refresh rate in the specification sheet.
Display features
Display features	Wide colour (P3); supports one billion colours	Wide colour (P3), one billion colours and True Tone; standard glass or optional nano-texture glass
Connections
Ports
Ports	2 × Thunderbolt 3, 4 × USB-A, SD card slot, Ethernet, headphone jack	2 × Thunderbolt 3, 4 × USB-A, SD card slot, Ethernet, headphone jack
Ethernet
Ethernet	1 Gb/s	1 Gb/s
External displays
External displays	Up to 2	Up to 2
Wi-Fi
Wi-Fi	802.11ac	802.11ac
Bluetooth
Bluetooth	4.2	5.0
Camera
Camera	FaceTime HD	1080p FaceTime HD
Back ports
Back ports	Four USB 3 ports; two Thunderbolt 3 USB-C ports with DisplayPort, Thunderbolt up to 40 Gb/s and USB 3.1 Gen 2 up to 10 Gb/s; SDXC, Gigabit Ethernet and 3.5 mm headphone jack; Kensington lock slot. Thunderbolt 2, HDMI, DVI and VGA require separately sold adapters.	Four USB-A ports; two Thunderbolt 3 USB-C ports with DisplayPort, Thunderbolt up to 40 Gb/s and USB 3.1 Gen 2 up to 10 Gb/s; UHS-II SDXC, Gigabit Ethernet and 3.5 mm headphone jack; Kensington lock slot. Optional 10Gb Ethernet supports 1/2.5/5/10Gb connections. Thunderbolt 2, HDMI, DVI and VGA require adapters.
External displays
External displays	Built-in display at full native resolution alongside one 5120 × 2880 display at 60 Hz with one billion colours, two 3840 × 2160 displays at 60 Hz with one billion colours, or two 4096 × 2304 displays at 60 Hz with millions of colours	One 6K or 5K external display, or two 4K displays; two 6K displays require Radeon Pro 5700 or 5700 XT. All listed external modes run at 60 Hz.
Speakers
Speakers	Stereo speakers; supports Apple iPhone headset with microphone	Stereo speakers
Microphones
Microphones	Built-in microphone	Three-mic array with directional beamforming; supports Hey Siri
Keyboard and mouse
Keyboard and mouse	Rechargeable Magic Keyboard and Magic Mouse 2; optional Magic Keyboard with Numeric Keypad and Magic Trackpad 2	Rechargeable Magic Keyboard and Magic Mouse 2; optional numeric keyboard and Magic Trackpad
Design and power
Type
Type	All-in-one	All-in-one
Weight
Weight	5.66 kg (better)	8.92 kg
Width × depth × height
Width × depth × height	528 × 175 × 450 mm	650 × 203 × 516 mm
Operating system
Operating system	macOS	macOS
Size and weight detail
Size and weight detail	Dimensions include the stand; weight varies by configuration. A built-in VESA mount version was also available.	Dimensions include the stand; weight varies by configuration and manufacturing process. A built-in VESA mount version was also available.
Power supply
Power supply	100–240 V AC, 50–60 Hz, single phase	100–240 V AC, 50–60 Hz, single phase
Materials
Materials	Recyclable aluminium enclosure; arsenic-free glass and mercury-free LED backlight	Recyclable, low-carbon aluminium enclosure; arsenic-free glass and mercury-free LED backlight
In the box
In the box	iMac, Magic Keyboard, Magic Mouse 2, power lead and Lightning to USB cable	iMac, Magic Keyboard, Magic Mouse 2, power lead, Lightning to USB cable and polishing cloth