We retrofit an old mac g3 destined for the e-waste pile with a water cooled ryzen 9950x and a 5080rtx. We managed to cram a full-sized atx motherboard, 2x 240m rads, an EK pump/res and managed to get everything to fit under the hood of the g3. We took the time and engineered a radiator stack that fits perfectly in the center line (center of gravity) of the chassis as well as a ton of custom 3d printed brackets, mounts, IO shields, etc.
System Spec:
CPU:9950x (corsair xc70 elite rbg cooler, AMD AI precision overclocked rather than manual OC)
GPU:RTX 5080 Astral (With EK Water Blocks Astral Liquid Cooler, slight overclock in afterburner)
RAM: 64GB (6400MT)OC
2x 240M Rad/Fans (1 rad for the gpu and 1 for the cpu)
EK Water Blocks – Pump Res Combo
Front IO – Retrofitted into iMac CD drive location
Rear IO – Maintained the original location of the rear IO of the Mac G3, but
retrofitted the IO with new IO options (6x rear usb3, 2x typec, ethernet, 3.5 audio)
Asus Rog Mini SFX PSU (1200w)
Idle Temperatures
CPU: 68-73C, GPU: 51-55C
Extreme Load Temps (prime95 stress test and gpu stress, 4k gaming average
CPU: 80-87C (no thermal throttling), GPU: 63-70C
Talking:
Have some content ready on the screen to flip through and talk about
maybe a few images to show the CG of the rad stack and the engineering that
went into it
Hello and thanks for tuning in, today im sharing a new custom pc build that I just finished for a good friend. the idea was initially simple – Try to build a gaming rig that dives into the upper echelon of 4k gaming, stays cool, and entirely fits inside the old mac chassis for a sleeper style of buid. Skip to the end for the final results.
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The first challenge was simply getting a full-sized ATX motherboard to fit inside the case. We decided to reuse part of the original metal chassis from the Mac. The only way we could get the motherboard to fit was by mounting it at roughly a 30-degree angle. At the same time, we also had to make sure the radiators would fit.
To address these issues, I designed and 3D printed custom parts to mount the radiators together in a single, compact radiator stack module. We positioned this stack toward the center of gravity of the Mac and bolted it securely into the bottom of the chassis. This solid radiator stack provided a surface to mount the motherboard at the required angle, allowing it to fit inside the case without any collisions.
You’ll notice the motherboard is tilted backward and bolted directly to the radiator stack. This setup helps keep everything stable and secure within the chassis. With the motherboard and radiator stack mounted, we turned our attention to the RTX 5080. There was no practical way to fit the GPU with its stock air cooler—those cards are massive—so we decided to liquid-cool the 5080. While doing so, we discovered that it fits perfectly on top of the motherboard, which helped save space.
Once the GPU was mounted, we started bending the pipes. This was one of the most challenging parts of the build, as many of the angles didn’t line up like they would in a standard, off-the-shelf case. Still, we managed to get everything to fit cleanly. We also squeezed the pump and reservoir into the very back of the Mac chassis.
The last major component was the SFX power supply, which we managed to mount nicely in the bottom compartment of the Mac’s chassis—keeping it completely contained within the original plastic shell.
With all the major components in place, we were finally able to power everything on and go through several pre-assemblies to check for clearance issues. Most importantly, we monitored the temps. At this point, I was confident that the custom liquid loop would keep everything cool, even though we were working with high-end hardware known for running hot.
After stress testing (which passed with flying colors), we even managed to hit some higher-than-stock benchmarks thanks to slight overclocks. At that point, we started feeling really good about the entire project.
As we entered the home stretch, the last thing to sort out was the front and rear I/O. I quickly modeled some components to mount everything. The rear I/O could use another revision, but it’s fully functional—and it has far more connectivity than the original G3 engineers could have ever imagined.
We also retrofitted the original Mac power button and LED to work with the new ASUS board. So the machine still powers on using the original button, and all the power and I/O remain in their original locations—except for the added CD drive I/O ports.
And that about wraps it up for the build! I hope you enjoyed the content as much as I enjoyed putting this one together.