Tom Hightower

Software Engineer and Photographer

iMac G4 Retrofit

2020-04-02

This guy bops

I'd like to start by shouting out Dremel Junkie, who has over the years posted a ton of super helpful information and documentation on iMac mods. I wish I'd discovered his site earlier on in the process, as it definitely would've saved many a headache and improved my internal layout on the machine. I also failed to take many photos during the initial disassembly, and Dremel Junkie was kind enough to let me rip a few.

These sorts of projects are all over. From this Raspberry Pi Super Nintendo to a Modern System in a 386 case to a Ryzen in a TRS80 to — perhaps my personal favorite — this PC in an old Philco radio, giving new life to an enclosure designed decades ago has a certain magic to it. I stumbled upon the chassis for this build while on Craigslist scavenging for parts for another build, and at $30 I couldn't say no. Even if I just used it as an external display or stuffed a Raspberry Pi into it for a low powered linux machine, I could get some use out of it (in retrospect this is a bad way to justify purchases).

Although its internals make it ancient in computer terms, the design is striking: unlike anything Apple had done before, with its flat panel screen and hemispherical base, and visually revolutionary in a way that few of their devices have been since. Just look how cute it is in the ad. Beautiful exterior and garbage components: perfect for a retrofit.

Initial Impressions

The device is a circa 2002 iMac G4 800 17" with a blazing fast 800MHz PowerPC processor, 256MB SDRAM, an 80GB HDD, and an included Apple Pro Mouse and Keyboard set. I knew when I got it that the display was nonfunctional, but I didn't mind having to upgrade the 1440x900 screen to a 1920x1200 one. My plan was to do a pretty simple swap and reuse both the backlight inverter in the display assembly as well as the LVDS wiring already running through the goose neck (there's some debate on what the pivot arm should be called, so I hope this video of geese eating apples will convince you). 17" replacement LCDs and their driver boards are easy to find online since it's a common size for larger laptops.

As a tribute to a respectable piece of hardware — and to see what would happen — I tried powering on the machine. The sounds of the cooling fan and hard disk spinning greeted me, but the blank screen was a little concerning. I wasn't expecting to see an output image, but the lack of a backlight gave a little insight into the problems I would later face.

All "mini VGA"

The only display output apart from the built-in screen is a mini-VGA port on the back. I had never used or even heard of it, and from what I could tell, the name can refer to a variety of different connectors used by various manufacturers. For my purposes it didn't seem worthwhile to spend extra time and money on fixing a system I was about to gut, so I said my farewells, powered it down for the last time, and got out the screwdrivers.

The port array on the back seems reasonably comprehensive at the time — other than the display interface. It's got 3 USB 1.1 ports (2.0 had just come out and wasn't adopted to the iMac until 2003), 2 Firewire 400 ports, an Apple Pro Speakers mini-jack, a phone jack for the 56k modem, a 100Mbps ethernet port, and a headphone jack. Experts speculate that the headphone jack was included simply so that when the 2003 model with optional bluetooth was released AirPod users would want to upgrade. However, there appears to have been a lack of communication between development teams since that module used Bluetooth 1.1 and the AirPods require at least 4.0. Crazy.

The teardown

This is just an overview of the process; if you're trying to recreate the mod, I highly recommend Dremel Junkie's website above.

I started by taking off the front of the display assembly, which houses the LCD panel and the backlight inverter, just to see what I was working with. Immediate disappointment. Not only was I getting no readout from the inverter on my multimeter, but I also found that the LCD was using a TDMS connection. This is a standard that powers both DVI and HDMI but is pretty uncommon as an internal display driver compared to LVDS.

On to the dome. Under the access plate (which incidentally is the only spot not using torx screws), we find the user-upgradeable RAM and airport card. I find it interesting that the internal RAM slot is a full length 135mm DIMM slot, but the one accessible by the user is a ~70mm SODIMM slot. I'm not sure that I've encountered mixed RAM form factors before, though I would imagine that giving the user access to only one slot for expansion was intended to 'simplify' the upgrade path.

Image courtesy Dremel Junkie

Digging further, the base of the dome can be removed, revealing the guts of the machine, which includes perhaps the only circular motherboard in a consumer desktop pc. I did a little searching but couldn't find any other examples. Theoretically you could upgrade up to 1GB of RAM in this guy since 133MHz PCI RAM could be found in up to 512MB modules, but a curious eBay search could only find PCI133 RAM as part of a bundle with an old server motherboard (and no SODIMMs).

The bulk of the space in the dome itself is taken up by the storage block, which is an aluminum cage with a disk drive mounted to one side and the 3.5" HDD mounted to the other. Though the tongue-out CD drive is cute, I would need to replace it since the original has an IDE interface, plus it takes up a ton of space, so I opted to scrap my dreams of circular storage mediums. I saved the hinging mechanism for the drive door in case I change my mind some day and want to rebuild it, but it's entirely aesthetics since I usually don't have much use for a disk drive.

Also contained in the dome is the power supply mounted on the side, an 80mm case fan, the Apple chime speaker, and a bunch of wires coming from the goose neck.

At this point I realized how much space I actually had to work with, and that just sticking in a Pi and display controller might be underkill.

Introducing the Intel NUC!

This little guy packs a punch at 115x111x36mm in its enclosure. It's basically laptop brains in a box with many features typically only available on desktop boards like extra USB/panel headers, serial headers, and no touchpad.

NUC with display control board and cage

The model I used is a Dawson Canyon NUC (7i7DNKE) with an 8th gen i7-8650U that I found used on eBay. I stuck 16GB of DDR4 ram and a 240GB M.2 drive in it, and it seems pretty happy. Since I wanted to load macOS on the drive, the included Intel M.2 WiFi card wouldn't work. Rather than spending $50 on a Broadcom chip, I found a USB3.1 Mac-compatible WiFi dongle and plugged her in. Unfortunately this means that I don't have the option to run antennas to the outside of the faraday cage, but I found I was getting pretty decent signal in my tests with the adapter positioned near a cutout.

The idea for using a NUC came from this Quinn Nelson video, and the majority of the hackintosh process for them is documented on TonyMac x86 (though I still had to do a lot of troubleshooting to get it to actually work).

The build

'tis but a scratch

I started with the display. I needed to replace the wires in the gooseneck, so I first tried to use the old ones to pull the new 30-pin LVDS and inverter power wires through — to no avail. The wires are stuck in place internally (enabling the neck to move freely), so I had to crack open the neck to avoid running them externally. The screws holding it together use a proprietary 3-point bit, so naturally I just Dremelled out a channel that I could stick a flathead driver into and it opened up like a charm. After carefully wrapping and routing the cabling, I attempted to put it back together. It did not close like a charm. Inside the goose neck is a massive spring that keeps the arm in position with the weight of the monitor on it, and that thing is hefty.

Image courtesy Dremel Junkie

I fought with the neck assembly for hours over multiple days. After almost giving up on the whole project a few times because of it, I was finally able to shimmy it into place using a steel allen wrench as a prybar (I actually had to do this twice because the first time I forgot the inverter wires). To anyone attempting: do not take apart the goose neck unless you absolutely must, and double check your work before closing it. Opening the neck appears to anger the goose.

At least you can't see it from the front

At this point I ran into a few problems. First, the panel I was trying to swap in had slightly bigger bezels than the old one, and while I could pretty easily modify the mounting hardware to accommodate it, there was no room left for the inverter. Additionally, there appeared to be a short in the inverter wires somewhere in the gooseneck because, while they had continuity, they couldn't carry a signal. Luckily the LVDS wires were unaffected by this. Rather than disassembling the neck for a third time, I conceded to stealthily mount the inverter on the back of the display assembly and to have just the four wires needed for inverter power running externally. At some point I'd like to go back and clean this up, but for now it's functional and not too unsightly.

Perhaps overkill but it works

After spending so much time fighting with the display connections, I was pretty excited to move back to the dome. I started by swapping out the existing case fan for a quiet 80mm Noctua NF-B9 with PWM control. Unfortunately, one thing the NUC is missing is extra fan headers, so I rigged up a little controller that adjusts the fan speed based on the internal case temperature using an Analog Devices temperature sensor. The controller is based around an Arduino micro (overkill) and just linearly scales the fan speed from 'off' to 'max' based on a temperature range. Since the cpu has its own cooler, this should be plenty to keep the system cool. Luckily the original fan was a standard 80x25mm case fan, so the new one just used the existing mounting hardware.

HDMI port might still need some work

Before working on shoving the guts in (but after checking that said guts would actually fit), I turned my attention to the rear I/O. As mentioned previously, the main I/O included 3 USB1.1, 2 Firewire 400, and a 100Mbps ethernet port, which just won't do for a modern system! The USB ports could have been reused for USB 2, but I ripped them out anyway and got some USB 3 extension cables to put in their place and run to the NUC, since it already has all the main ports I want accessible. I had to trim the ends a bit with the Dremel so that they fit next to each other in the existing holes, but I think they turned out about as well as I could have hoped given what I'm doing to the poor thing. They're all stuck in place with some high-tech thermoplastic adhesive.

I wasn't using anything on the original motherboard besides the rear I/O, and I hadn't used the Dremel in several minutes, so I got it back out and cut the whole thing in half.

It took a whole team to make it round, but 5 minutes with a Dremel to undo it

Much better.

The ethernet port got a similar treatment to USB. I fitted a cat-6 RJ45 extender that ran to the 1Gbps port on the NUC. The last main port I cared about was HDMI. The extender end wouldn't fit where the mini-VGA port was, but after cutting out the plastic column between the dual Firewire ports it fit there just fine. My last alteration was adding some wires to the momentary switch behind the original power button so that it could still be used. For now I left the mini-VGA, DSL, Pro Speaker, and headphone jacks alone since I didn't have anything better to put there. I'd like to use the original headphone jack, but at the moment my macOS install isn't working with HDMI audio output, so I'm going to try to fix the software before I do the hardware. I do have audio through this USB audio adapter, so if all else fails I might just put that inside and wire it to the built-in headphone jack.

The "Guts": Display board, power supplies, and NUC mounted to the cage

On to the guts! I salvaged the drive carrier to mount everything on since it already had holes that lined up with the screw holes of the chassis. It's lightweight aluminum, so I was able to cut off any bits that blocked my hardware and then drill holes for the standoffs that the display and fan controllers would mount to. I left the NUC in its case because it was the easiest thing to do at the time, but it would've been more efficient for both space and cooling to remove the case and mount it like the other boards. Besides the NUC, fan controller, and display board, the cage also holds power supplies: an 18v brick for the NUC and a 12v board for the display, which also powers the fan. The fan controller recieves 5v from a regulator built into the display control board.

The final touch before shoving everything in was to add a monitor power button and light to the front. Since at the moment I'm not using the disk drive door, I sealed it to the surrounding plastic, added an indicator LED behind it to glow through, and cut a small hole for a tact switch. These got wired to the display control board. I thought about doing this for all of the OSD buttons that the control board exposes, but I don't see myself messing with the OSD controls enough to justify further ruining the clean finish on the front.

Time to put it all together. The original power button got wired to the fan header before I closed up the NUC, so I left some slack on it so that I could still work on the two halves separately while putting in the main block. I left a lot less slack on the LVDS wires coming from the goose neck so that there wouldn't be anything to get caught in the fan, so I plugged those in as I was lowering the block into the dome. After that, I just needed to plug in all of my port extenders, wire the two power supplies into the original AC plug, and cable manage enough to safely close the bottom.

Software

This was my first venture into Hackintoshes, but between the TonyMac guide linked above and others (including this good one from Hackintosher) I was able to get it up and running in a couple of hours with most things working. For simplicity's sake I got most of the kinks worked out before actually sticking the NUC into the dome.

Version info; the G4 is running the latest version of Mojave

Working:

  • USB Audio
  • USB/HDMI ports
  • Ethernet
  • WiFi
  • Sleep and Wake
  • App Store, iMessage

Not Working:

  • HDMI Audio
  • Bluetooth (no bluetooth adapter)
  • DSL 56k modem

I don't want to talk a lot about the benchmarks, because this is first and foremost a project about giving new life to a beautiful old machine.

She does hold her own though.

I compared it to a late-2018 Mac Mini with an i7-8700B that was benchmarked on Geekbench. It's worth noting that the Mac Mini compared only has 8GB of ram, but it also has a 6-core desktop i7, so that heavily influences the multi-core score.

So, the G4 isn't going to be setting any records, but I spent just under $400 on this whole build, and the i7 Mac Mini I'm comparing it to retails for around $1500.

Perhaps a more fair comparison is against the i3 Mac Mini, which retails for $799, only about double this build's cost. It has a 4-core desktop i3 and 8GB of ram.

Would it have been a lot easier and more time-efficient to just buy a Mac Mini? Yes.

Would I be willing to pay an extra $400 for something less powerful that doesn't look as cool? No.

If you've done/want to do a project like this or if you have any questions or comments, please reach out!