Apple iMac (Retina 4K, 21.5-inch, 2019) vs Apple iMac (Retina 4K, 21.5-inch, Late 2015)

Every spec side by side, from each maker's published figures.

Better figure, where one is clearly better

iMac (Retina 4K, 21.5-inch, 2019) compared with iMac (Retina 4K, 21.5-inch, Late 2015)
AppleiMac (Retina 4K, 21.5-inch, 2019)AppleiMac (Retina 4K, 21.5-inch, Late 2015)
Overview
ReleasedMarch 2019October 2015
Performance
ProcessorIntel Core i3-8100, Intel Core i7-8700 or Intel Core i5-8500Intel Core i5-5675R or Intel Core i7-5775R
CPU cores4 or 64
CPU threads4, 6 or 12–
GraphicsRadeon Pro 555X (2 GB GDDR5), Radeon Pro 560X (4 GB GDDR5) or Radeon Pro Vega 20 (4 GB HBM2)Intel Iris Pro Graphics 6200
Memory8 GB, 16 GB or 32 GB (better)8 GB or 16 GB
Storage256 GB to 1 TB256 GB to 2 TB (better)
CPU3.6 GHz quad-core Core i3 without Turbo Boost, or 3.0 GHz six-core Core i5 with Turbo Boost up to 4.1 GHz; both configurable to 3.2 GHz six-core Core i7 with Turbo Boost up to 4.6 GHz3.1 GHz quad-core Core i5 with Turbo Boost up to 3.6 GHz; configurable to 3.3 GHz quad-core Core i7 with Turbo Boost up to 3.8 GHz
GPURadeon Pro 555X with 2 GB GDDR5 in the lower base; Radeon Pro 560X with 4 GB GDDR5 in the upper base, configurable to Radeon Pro Vega 20 with 4 GB HBM2–
Memory type8 GB standard, configurable to 16/32 GB; lower base uses 2400 MHz DDR4 and upper base 2666 MHz DDR4. Memory is not readily user-accessible.1867 MHz LPDDR3 onboard memory; 8 GB standard, configurable to 16 GB at purchase
Storage typeThe current Apple sheet lists 256 GB SSD or 1 TB Fusion Drive for both bases, and these are the configurations shown. Apple made SSD storage standard in August 2020. Launch reviews describe a 1 TB hard drive in the lower base and 1 TB Fusion Drive in the upper base, with larger SSD options (Macworld and TechRadar); these historical options are not flattened into the current matrix.1 TB 5400-rpm hard drive; optional 1 TB or 2 TB Fusion Drive, or 256 GB or 512 GB SSD. The 1 TB Fusion Drive combines a hard drive with 24 GB of flash; the 2 TB version has 128 GB of flash.
Display
Screen size21.5″21.5″
Resolution4096 × 23044096 × 2304
PanelIPS LCDIPS LCD
Brightness500 nits–
Display typeLED-backlit Retina 4K display; IPS panel confirmed by EveryMac; Apple does not publish native refresh rate in this model’s specification sheetLED-backlit Retina 4K display with IPS technology and support for millions of colours
Display featuresWide colour (P3); supports one billion coloursP3 colour gamut; Apple does not publish brightness or refresh rate in this model's specification sheet
Connections
Ports2 × Thunderbolt 3, 4 × USB-A, SD card slot, Ethernet, headphone jack2 × Thunderbolt 2, 4 × USB-A, SD card slot, Ethernet, headphone jack
Ethernet1 Gb/s1 Gb/s
External displaysUp to 2 (better)Up to 1
Wi-Fi802.11ac802.11ac
Bluetooth4.24.0
CameraFaceTime HDFaceTime HD
Back portsFour 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; SDXC, Gigabit Ethernet and 3.5 mm headphone jack; Kensington lock slot. Thunderbolt 2, HDMI, DVI and VGA require separately sold adapters.Four USB 3 ports, two Thunderbolt 2 ports with Mini DisplayPort output, SDXC card slot, Gigabit Ethernet, 3.5 mm headphone and optical digital audio output; Kensington lock slot. HDMI, DVI, VGA and dual-link DVI require separately sold adapters.
External displaysBuilt-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 coloursBuilt-in display at full native resolution alongside one external display up to 4096 × 2304; extended desktop and video mirroring
SpeakersStereo speakersStereo speakers; supports Apple iPhone headset with microphone
MicrophonesBuilt-in microphoneDual microphones
Keyboard and mouseRechargeable Magic Keyboard and Magic Mouse 2; optional Magic Keyboard with Numeric Keypad and Magic Trackpad 2Rechargeable Magic Keyboard and Magic Mouse 2; optional Magic Trackpad 2 with Force Touch
Design and power
TypeAll-in-oneAll-in-one
Weight5.48 kg (better)5.68 kg
Width × depth × height528 × 175 × 450 mm528 × 175 × 450 mm
Operating systemmacOSmacOS
Size and weight detailDimensions include the stand; current Apple sheet lists 5.48 kg and warns that weight varies by configuration. Launch reviews tested heavier hard-drive/Fusion configurations. A built-in VESA mount version was also available.Dimensions include the stand; weight varies by configuration. A built-in VESA mount version was also available.
Power supply100–240 V AC, 50–60 Hz, single phase100–240 V AC, 50–60 Hz, single phase
Noise–Apple's 3.1 GHz Core i5, 8 GB, 1 TB hard-drive test configuration: operator-position sound pressure 11 dB at idle and wireless web, 11.5 dB during hard-drive seek
MaterialsRecyclable aluminium enclosure; arsenic-free glass and mercury-free LED backlightRecyclable aluminium enclosure; arsenic-free display glass; mercury-free LED backlight
In the boxiMac, Magic Keyboard, Magic Mouse 2, power lead and Lightning to USB cableiMac, Magic Keyboard, Magic Mouse 2, power lead and Lightning to USB cable

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