Along with a spectacular display, the 21.5" Retina 4K iMac has some new age specs:

3.1 GHz quad-core Intel Core i5-5675R (Turbo Boost up to 3.6 GHz)

8 GB of 1867 MHz LPDDR3 RAM

Intel Iris Pro Graphics 6200

1 TB (5400-rpm) hard drive, configurable up to 2 TB Fusion Drive or 512 GB of flash storage.

802.11ac Wi-Fi + Bluetooth 4.0

Shiny new EMC number, 2833 (same ol' model number A1418)

This new display (first image) packs quite a punch, especially compared to the non-Retina iMac (second image). The difference is like pixelated night and seamless day.

We got up-close and personal with the a few of the (over 9 million) pixels in the 4K IPS display. Each is made up of a red, green, and blue strip—vary those and you get a colored pixel.

This 4,096 x 2,304 pixel display packs more than 4.5 times the number of pixels in a standard 21.5" iMac display.

Double the opening tool, double the opening speed! We've done so many of these we figure we gotta step our game up a bit.

The display cable is now slightly wider to support all those extras pixels. 16.4 mm over the 12.4 mm of the non-Retina 21.5".

We also note a new rubber bumper stuck to the fan's top screw—likely to provide a little extra support for all those heavy new pixels.

Unlike other iMacs, this one's packing a DCI-P3 display—one of the first available to consumers—so we're quick to dispatch this shiny metal cover so obviously concealing some delicious chips.

Like its siblings, this 4K display has some control hardware tucked away behind the front panel:

Texas Instruments TPS65168 High Resolution, Fully Programmable LCD Bias

Texas Instruments TPS54320 4.5 V to 17 V Input, 3 A Synchronous Step-Down SWIFT Converter

Texas Instruments TPS54218 4.5 V to 17 V Input, 3 A Synchronous Step-Down SWIFT Converter

Parade Technologies DP665 LCD Timing Controller (the same found in last generation's 27" 5K model)

Texas Instruments NH245 55K G4

Texas Instruments BUF16821 Programmable Gamma-Voltage Generator and Vcom Calibrator

Turning our attention to the interior of the iMac, we find exactly what you would have found in last year's 21.5" iMac—how dull.

As usual, Apple sticks to its guns on its hard drive, fan, and speakers—retaining their designs between generations.

Apple is back to their old ways: In 2012, when Apple launched the thin-edged iMac, our base-level iMac had empty solder pads where a Fusion Drive's SSD slot might live.

The following year, our teardown unit arrived with an empty slot, ripe for the upgrade.

The curved heatsink is a bit beefier than we saw earlier this week, and a return to the 2013 design; perhaps helping that new Broadwell CPU find cooler pastures.

This little machine has plenty of brawn, but we're itching to check out its brains too:

Intel SR2AJ Core i5-5675R 3.1 GHz Processor (4M Cache, TurboBoost up to 3.60 GHz) with Intel Iris Pro Graphics 6200

Samsung K4E6E304EE-EGCF 16 Gb LPDDR3 1867 MHz SDRAM (4 chips for a total of 8 GB)

Broadcom BCM5776 Gigabit Ethernet Controller

Texas Instruments LM4FS1EH SMC

Texas Instruments HD3SS213 5.4Gbps DisplayPort 1.2a 2:1/1:2 Differential Switch

Fairchild FDMF6808N Extra-Small, High-Performance, High-Frequency DrMOS Module (presumably a new iteration of FDMF6708N)

Intel DSL5520 Thunderbolt 2 Controller

Cirrus Logic 4208-CRZ Audio Controller

Delta 8904C-F Filter

Vimicro VC0359 Camera Processor

Intersil ISL6372CRTZ PWM Controller

Winbond 25064FVIQ

International Rectifier IRFH3702 30V Single N-Channel HEXFET Power MOSFET

iMac Intel 21.5" Retina 4K Display Repairability Score: 1 out of 10 (10 is easiest to repair)

Cutting the tape to open the iMac isn't too hard (with the right tools), but it must then be replaced to complete any repair.

The RAM is still soldered to the logic board—you're stuck with what you bought.

The Fusion Drive connector is missing from the logic board, killing all hope of storage hacking.

The CPU is soldered to the logic board, and cannot be replaced or upgraded.

The glass and Retina Display are fused together, increasing the cost of replacement.