Power Mac G4 MDD ATX Conversion
16 April 2024
During normal operation of my Power Mac G4 MDD (Mirror Drive Door), I noticed it becoming increasingly unstable. It would crash often, USB devices wouldn't receive power and it eventually became so unreliable I couldn't use it.
I decided to remove the power supply and check it's current state. Upon opening the power supply I noticed that many of the capacitors were bulging and beginning to leak, and this explains why I was having so many problems with stability.
The Mac OS 9 Lives user Fdb/FBz/aBc provided me an excellent diagram of my particular power supply which noted each capacitor type/value for replacement. While I do plan to refurbish the original power supply eventually, I needed a quick fix and since I already had a MDD to ATX adapter this was the easiest option.
I found that SFX seemed to be the best PSU (power supply) form factor in terms of it fitting nicely inside the MDD, and allowing room for PCI cards.
Here's the equipment I purchased for this project:
SilverStone SX650-G |
Power Mac G4 MDD ATX Adapter |
ATX extension cable |
Considerations
ADC Monitors
One thing to note when purchasing a power supply is that some/most ATX PSUs don't have the +25v configuration required for ADC power. This means that the Mac will no longer be able to power ADC monitors (Apple Cinema Displays). I don't have an ADC monitor to test with the Silverstone PSU, but if it's not present you can pull and move pins to the +25v spot.
Deep Sleep
Another consideration is that some power supplies don't supply the 5v needed for deep sleep. This means that your Mac won't be able to fully enter sleep mode, or it may experience freezes when waking up. Thankfully, the SilverStone SX650 does provide the 5v required for deep sleep.
Video Card Support
Some video cards won't work unless you have made adjustments to supply the +25v needed for ADC. I've had limited success with AGP video cards that have an ADC port, and they seem to cause issues with deep sleep, with the exception of the NVIDIA GeForce4 MX 400. The PCI cards I have tested allow deep sleep, but often display a corrupted image when waking from sleep. This may be due to the power supply not providing enough power to the PCI slots while the computer sleeps.
Here are the cards I have tested with the SilverStone SX650:
Video Card | Interface | Memory | Functions with SX650 PSU | Deep Sleep Support | Image Corruption on Wake |
|---|---|---|---|---|---|
NVIDIA GeForce 4MX | AGP | 64MB | Yes | No | N/A |
NVIDIA GeForce4 MX 440 | AGP | 32MB | Yes | Yes | None |
ATI Radeon 9000 | AGP | 64MB | No | N/A | N/A |
ATI Radeon 7000 Sapphire | PCI | 64MB | Yes | Yes | Yes |
ATI RV6P-NA3 (PC Flashed) | PCI | 32MB | Yes | Yes | Yes |
If you are going ahead with an ATX conversion I recommend using the NVIDIA GeForce4 MX 440.
* The functional ATI PCI cards required the 2002 driver update before they were fully functional.
* The NVIDIA GeForce4 MX 440 works best with the Mac OS 9.2.2 base installation drivers. The 2002 drivers can sometimes result in a black screen when extensions start loading.
USB Issues
I've noted that some USB devices will cause issues with this setup. For example, keeping a USB drive plugged in can cause lockups when booting into the Finder, shutting down the computer, coming out of full screen applications and reloading the Finder, and when Bus scanning occurs (e.g. opening Apple System Profiler). I did experience some of this behaviour before replacing the PSU so it may not be 100% related. Leave a comment if this hasn't been an issue for you.
ATX Extension Cable
I found the ATX cable extension to be necessary for this conversion. When I originally installed the MDD to ATX cable and closed the case, it would pull on the PSU cable enough so that the CPU would lose connectivity with some pins, and it's performance would be crippled. Using the ATX extension prevents this from happening and gives the cable plenty of wiggle room to get things sitting nicely.
Installation
1) Connect the ATX to G4 cable to the power supply, and the ATX extension to the ATX to G4 cable. |
2) Add some protection/padding around the cables. There's lots of sharp edges within the case that can pierce the PSU cables. |
3) Remove the CPU fan and pull the cable through the chassis to the PSU connector on the logic board. |
4) Install an exhaust fan to keep the PSU cool. I used a Noctua NF-A4x10 PWM 40x40x10mm which seems to be sufficient for now. |
5) I used the rubber standoffs included with the Noctua fan and pullled them through the vents. These keep the fans in place without altering the case and reducing noise. |
6) After plugging in the PSU cable, Install the CPU fan again and place the PSU in it's original spot, while ensuring that the intake fan is facing where the PCI cards will be when the case is closed. |
7) The exhaust fan is connected to a PCI PWM fan controller card. This gives me the ability to adjust the fan speed. |
8) The finished state after installing the PSU and exhaust fan. |
Finishing
The SilverStone PSU fits almost perfectly for the power cable do remain in it's original position, but the socket is oriented the wrong way. This means you have to thread the power cable inside the case slightly to plug it in. I found this to be a good thing because since the PSU's intake fan receives all of the heat produced by the PCI cards, there is enough room to attach some small exhaust fans to the case for expelling the heat. I attached a Noctua fan just above where the power cable enters which provides excellent airflow.
There's also nothing to secure the power supply to and I found that wedging in some foam above it kept it secure while sitting in place of the old power supply.
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