iMac Intel 21.5" Retina 4K Display 2017 Teardown
By Blake Klein • Difficulty: Moderate
Introduction

500 nits, 1 billion colors, and two Thunderbolt ports—that's everything, right? Not so fast. Apple already told you about the updated iMac 4K's fancy specs, but we're here to reveal what wasn't in the press release. It's time to take this all-in-one and split it into a whole lotta pieces—join us for a teardown of the mid-2017 iMac 4K.

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iMac Intel 21.5" Retina 4K Display 2017 Teardown
  • Well this exterior certainly isn't giving much away, but you can't always judge a book by the aluminum-and-glass shell of the iMac that you're reading it on. Let's start with what we know:
  • 3.0 GHz quad-core Intel Core i5 (Turbo Boost up to 3.5 GHz)
  • 8 GB of 2400 MHz DDR4 memory
  • Radeon Pro 555 GPU with 2 GB of VRAM
  • 1 TB (5400-rpm) hard drive
  • 802.11ac Wi-Fi and Bluetooth 4.2
  • 43% brighter display (500 nits) with 4096 × 2304 resolution and P3 wide color gamut
Step 2
  • A peek at the back reveals a bevy of ports. First, the usual suspects: a headphone jack, SD card reader, four USB ports, and an ethernet jack.
  • The un-usual suspects? This iMac's sporting two Thunderbolt 3 ports. These support double the bandwidth of the previous generation—each of these ports can push data at 40 Gbps.
  • That's enough throughput to drive four 4K external monitors—although with this hardware configuration, Apple says we're limited to two.
  • How are we supposed to get by with a total of just three 4K displays? How?
  • Confirming our suspicion that this is mostly a 2015 iMac with a facelift, this unit sports the same model number (A1418), but with a new EMC: 3069.
Step 3
  • We grab our pizza cutter iMac Opening Wheel and go to town. Then, we bring it back home and use it to split open our fancy new iMac.
  • 'Round and 'round we go, and the adhesive securing the display perimeter goes kaput.
  • When Apple introduced this form factor in 2012, replacing the much-loved magnets, we were sad and confused. Since then we've learned its secrets, and now we're on board with how easy this adhesive is to slice through.
  • We'd love to see Apple implement something like this in their other product lines.
  • After a familiar opening procedure, we get our first peek inside.
Step 4
  • With all the glass and pixels out of the way, we immediately pick out some subtle updates.
  • First, the logic board has grown—encroaching on territory formerly held down by the right speaker, and even expanding towards the fan a bit.
  • Even more notable, there's a conspicuous heat sink mounting plate sprawled out in the middle of the board. Funny, the old heat sink didn't need one of those...
  • Lastly, near the center of the bottom display bezel, just beneath the glass, there's a microphone! Whose ribbon cable routes right over the top of a screw, which is pretty weird.
Step 5
  • Well, this part of the refresh is less refreshing than we'd like—the right speaker is no longer immediately removable. It's trapped pretty solidly by the new logic board contours.
  • No big deal; it just means your favorite set of iMac repair guides won't fully apply to this model. We'll get to work on that for you.
Step 6
  • The rest of this iMac comes apart pretty much the way we expect, and we dispense with the power supply, hard drive, and fan without fuss.
  • And with a bit more elbow grease, we shimmy the logic board out of its slot to reveal ... removable RAM? We can hardly believe our eyes.
  • Yep, those are SO-DIMMs. Two of them.
  • Slightly less excitingly, there's also an exciting split heat sink. But seriously look at that RAM!
Step 7
  • It may not be as accessible as the (dead simple) RAM hatch found in the 27" iMacs—but still, this is a major win for upgradability over all the 21.5" iMacs with soldered RAM that we've encountered in recent years.
  • Before moving on, we take a moment to scope out the silicon these memory modules have to offer:
  • SK Hynix H5AN8G6NAFR 8 Gb DDR4 SDRAM (4 × 8 Gb = 4 GB per DIMM, 8 GB total)
Step 8
  • This new heat sink design has us intrigued. What's hiding under there?
  • Warranty voiding stickers on the heat sink screws? That's odd. Could that mean...
  • Yes! The CPU is modular, too! It lifts right off with the heat sink, revealing a standard LGA 1151 CPU socket.
  • Again, this isn't the most accessible thing in the world—it's flipped onto the backside of the logic board, trapped behind a lot of other components, and buried under a glued-down pane of glass—but for the first time in years it's possible to replace or upgrade the CPU without a reflow station, and that's a big win.
Step 9
  • This CPU is quite well thermally-pasted into its heat sink; prying it out was surprisingly tough. Someone wants this processor to keep cool.
  • Finally, we're face-to-face with the star of this teardown: an Intel SR32W Core i5-7400 Kaby Lake CPU, 6M Cache, up to 3.50 GHz.
  • Looking at the rest of the Kaby Lake lineup, we're actually not seeing any desktop-class CPUs in a BGA package. Maybe Apple reverted to a socketed CPU because that's all Intel is offering at the moment.
  • But with Apple's clout and famous negotiating skills, you'd think they could get a soldered CPU if they wanted. Plus there's that mysterious modular RAM...
  • Have you been hearing our pleas, Apple?
Step 10
  • The final bit of interesting modularity on this board: a CMOS battery.
  • With all this new modular hardware, it almost looks like they ran out of space for this guy. It's hilariously placed vertically in this cute little battery toaster slot.
  • Side note: please do not put batteries in the toaster.
  • Or toast in your iMac for that matter...
Step 11
  • Now that it's stripped of all accoutrements, we can ID this logic board's silicon:
  • Intel LGA 1151 CPU socket
  • AMD Radeon Pro 555 GPU
  • SK hynix H5GC4H24AJR-ROC 4 Gb GDDR5 2400 MHz SDRAM (4 Gb × 4 for a total of 2 GB VRAM)
  • Broadcom BCM5776 Gigabit Ethernet Controller (as seen in the 2015 iMac revisions)
  • Texas Instruments CD3215C00 (also seen recently in the 15" MacBook Pro)
  • Intel SR2C9 platform controller hub
Step 12
  • Flip the board for more chips? Don't mind if we do:
  • Vimicro VC0359 camera processor
  • Cirrus Logic CS42L83 audio controller
  • MXIC MX25L6473E 64 MB serial flash memory.
  • Intersil 95828 HRTZ X707DMB
  • NXP 6142E
  • Intersil ISL6277A multiphase PWM regulator
  • Fairchild FDH10CJ
Step 13
  • Turning our attention back to the display: the fancy new panel comes courtesy of LG (who also made the fancy old panel).
  • And that famously W-Fi allergic external monitor...
  • This particular ultra-high def beauty is model LM215UH1-SDB1.
  • Now moving to the display chips, read on!
Step 14
  • Take a peek at what powers those popping pixels:
  • Texas Instruments SN74LVC8T245 8-bit dual-supply bus transceiver
  • Texas Instruments BUF16821 Programmable Gamma-Voltage Generator and Vcom Calibrator
  • Parade Technologies DP665 LCD Timing Controller (the same found in the last generation iMac 4K)
  • We assume this is an Apple modified version of the DP663
  • Texas Instruments TPS54218 4.5 V to 17 V Input, 3 A synchronous step-down SWIFT converter
  • Texas Instruments TPS54320 4.5 V to 17 V Input, 3 A synchronous Step-Down SWIFT converter
  • Texas Instruments TPS65168 High Resolution, Fully Programmable LCD Bias
Step 15
  • Previous iMacs featured a dual-mic setup, with two microphones hiding behind the front-facing camera. Two microphones allows the device to filter out ambient noise and produce a cleaner signal.
  • This year, it seems Apple switched to a single microphone—and moved it to the bottom of the display, behind the glass.
  • Perhaps they've improved their signal processing enough to make do with one and save some pennies.
  • We'll wait to hear from the early adopters if the new setup is any better or worse.
Step 16
  • And that's that!
Final Thoughts
  • iMac Intel 21.5" Retina 4K Display 2017 Repairability Score: 3 out of 10 (10 is easiest to repair)
  • The CPU and RAM—two of the components you are most likely to upgrade at some point—are both modular.
  • The standard 2.5" SATA hard drive is fully upgradable—though you can't add a blade SSD thanks to an empty pad on the logic board.
  • 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.
  • Most replaceable components (like the RAM) are buried behind the logic board, meaning you'll have to take apart most of the iMac just to gain access to them.
  • The glass and Retina Display are fused together, increasing the cost of replacement.