Powermac G4 MDD AIO Watercooling Concept/Project

Hi everyone,

I’ve been quietly tinkering with a project and wanted to see if there’s interest in a small-run kit.

Quick background: my fiancée and I run the PC-hardware YouTube channel “tektherapy,” and I previously operated a console-mod shop focused on BGA rework/soldering. In short, I have solid access to parts and fabrication—which helps here.

The project: adapting a 120 mm PC AIO liquid cooler for the Power Mac G4 MDD. My test unit is a dual 1.25 GHz overclocked to 1.5 GHz. I’ve mounted a 120 mm radiator in front of a new, quieter left-side exhaust fan near the HDD tray. Even at low fan RPM, peak CPU temps drop noticeably, and the loop keeps temps from spiking quickly under load.

Next steps (hardware I’m designing):

• Clean radiator clamps/brackets for a proper MDD fit
• A CPU bracket/adapter to mount the AIO pump with minimal fuss

Quicksilver support may be possible (layout permitting), but I’m focusing on MDD first—especially given the stock noise levels. With the added cooling headroom, higher overclocks should also be more achievable; these AIOs are designed for far higher-TDP modern CPUs.

Related ideas (for later): I’ve already swapped the PSU fans for Noctuas, which helped. I’m also considering an SFX-PSU mounting bracket to run modern SFX-PSUs with ATX cable adapters—ideally without losing ADC. (Working on a curcuitry for this)

Proposal: if there’s interest, I can produce a kit that includes a compatible 120 mm AIO plus laser-cut metal mounting brackets (current prototypes are 3D-printed; production would be metal for stability).

Would this be useful to folks here?

I’ll add photos to this thread soon—I’m traveling at the moment and finally had a chance to post.
For the admins: this isn’t self-promotion; I’m gauging interest in a community-useful solution.

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An SFX+ADC kit for the MDD would definitely be useful. I like to avoid liquids inside computers though, even sealed AIOs.

treellama said:

An SFX+ADC kit for the MDD would definitely be useful. I like to avoid liquids inside computers though, even sealed AIOs.

Click to expand...

Been using hundreds (literally) over the last decade. I never had any leakage issues. The only thing on older AIOs is pumps sometimes dies. Especially on cheaply manufactured chinese off-brand pumps.

These days it's just the norm in the PC Industry. Which gave me the whole idea.

It's not the leakage in AIOs, it's the lifespan, in a forum where people expect computers to work for decades!

Hello, welcome to the forum. I would be interested in a more refined cooling setup. How are you measuring temperatures? Is the main MDD fan removed, or is this now cooling the liquid radiator? One of the main problems I've found with using PC coolers on Dual G4 boards is the spacing of the two chips is usually wider than the contact area of the cooler. I've found a few that were wide enough, but these obviously need customization anyway to fit. Here is one example:

68kmla.org/bb/index.php?threads/mdd-heatsink-upgrade.41488/

Another nice feature of water cooling is the water blocks can be much smaller and would be easier to attach to the CPUs without damage. Normally, carefully balancing a big piece of metal on a little piece of silicon can be tricky.

treellama said:

It's not the leakage in AIOs, it's the lifespan, in a forum where people expect computers to work for decades!

Click to expand...

Nothing lasts for decades, even our trusted "retro-machines" .. without some TLC

We always will need to re-work components, swap Caps, swap PSUs etc.
I have been in the industry for 25+ years now repairing old machines (beside working on new ones) and i am constantly re-working / fixing my own machines. Just recently recapped my FM Towns to prevent some leakage.. it's always an ongoing thing imo.

herd said:

Hello, welcome to the forum. I would be interested in a more refined cooling setup. How are you measuring temperatures? Is the main MDD fan removed, or is this now cooling the liquid radiator? One of the main problems I've found with using PC coolers on Dual G4 boards is the spacing of the two chips is usually wider than the contact area of the cooler. I've found a few that were wide enough, but these obviously need customization anyway to fit. Here is one example:

68kmla.org/bb/index.php?threads/mdd-heatsink-upgrade.41488/

Another nice feature of water cooling is the water blocks can be much smaller and would be easier to attach to the CPUs without damage. Normally, carefully balancing a big piece of metal on a little piece of silicon can be tricky.

Click to expand...

Hi Herd,

Long time no hear!

To your questions:

• Exhaust fan / fitment
  I removed the original exhaust fan and swapped in a Noctua 140 mm fan mounted on the 120 mm radiator. The radiator is small enough that the door still closes normally.
• CPU die coverage
  The AIO’s copper plate is wide enough to cover both CPU dies—I tested this early on—so no extra spreader/adapter plate is needed.
• Temperature measurements
  I’m measuring with two K-type probes placed near the CPU dies, with the system fully closed. I’ll update the thread with the current prototype setup and screenshots of load/idle temps in a few days. Since i am currently out of the country.
• Fan/Pump control
  Right now the Noctua fan is fixed around 900 RPM, and the pump runs at 100% (not audible with the case closed). I plan to add a simple PWM controller with a thermal probe to ramp fan and pump as needed. I’ve also run the Noctua as low as ~500 RPM and still saw good temps—never hitting vmax.

I don't know if you'll reach the critical mass threshold of interest to produce the whole kit at the ideal scenario level, but I'd buy the stuff you're describing if you do. Maybe more than one, even.
If it doesn't make it to the metal phase of production, I'd at least be willing to chip in for the plans to print em.
Are you experimenting with typical corsair stuff or something more uncommon? also LGA, AM#, TRX?

Hey!

I’ve been experimenting with sturdier infills on my prints since I recently upgraded to a Bambu Lab H2D Pro. I want to see if I can make the mounting adapter rigid enough so I don’t have to go down the route of laser-cut metal brackets.

As you might know, most AIOs use Asetek pumps because of their patent situation.

Right now I’m testing with a very small 120 mm radiator (with an Asetek Gen 8 pump-head) that’s basically not much bigger than the fan next to the HDD tray in the MDD. It’s the kind of unit you find in a lot of “generic” AIOs on the market.

Honestly 80% of them are Asetek-based, except for some of the odd ones from China / Temu / AliExpress.

The only thing I really had to make sure of was that both CPU dies are covered, which actually worked with the unit I’m testing. Some AIO pump heads are smaller and don’t cover both dies properly.

The nice part: this way I don’t need an extra copper shim/plate.

The mounting bracket is basically screwed onto the original mounting holes of the AIO pump, so I’m not reusing/adapting the stock LGA/AM5 brackets. That way it stays a clean, self-contained solution.