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Comprehensive Guide to Converting G5 Quad to Air Cooling

mac57mac57

mac57mac57

macrumors 6502a
Original poster
Aug 2, 2024
586
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Myrtle Beach, SC
Hello All,

As promised, I have been documenting everything as I have gone through the process of converting my Power Mac G5 Quad from Liquid Cooling to Air Cooling. The results were richly satisfying: all four CPUs idling in the high 30 C area, all CPU fans running at their default low idle speeds.

I have written a document that I hope is a comprehensive A-Z guide to converting a G5 Quad from liquid to air cooling. This is a large'ish document (40 pages) but it is rich with images and photos, which pushes up both page count and file size.

I would like to encourage the more knowledgeable readers here at MacRumors to go through it critically and reply back with comments. I would like this document to be as accurate as possible - it is my contribution back to MacRumors for all the help you have given me as I went through this task. I hope that this guide may help many others do the same thing.

The guide can be viewed/downloaded from:

https://inverary.net/LCS/Power Mac G5 Quad Air Cooling, A-Z Guide, v0.3.pdf

The original Word document is in the same place - just change the ".pdf" at the end of the URL to ".docx".

Comments and feedback MOST welcome!
 
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mac57mac57 said:
Hello All,

As promised, I have been documenting everything as I have gone through the process of converting my Power Mac G5 Quad from Liquid Cooling to Air Cooling. The results were richly satisfying: all four CPUs idling in the high 30 C area, all CPU fans running at their default low idle speeds.

I have written a document that I hope is a comprehensive A-Z guide to converting a G5 Quad from liquid to air cooling. This is a large'ish document (40 pages) but it is rich with images and photos, which pushes up both page count and file size.

I would like to encourage the more knowledgeable readers here at MacRumors to go through it critically and reply back with comments. I would like this document to be as accurate as possible - it is my contribution back to MacRumors for all the help you have given me as I went through this task. I hope that this guide may help many others do the same thing.

The guide can be viewed/downloaded from:

https://inverary.net/LCS/Power Mac G5 Quad Air Cooling, A-Z Guide, v0.1.pdf

The original Word document is in the same place - just change the ".pdf" at the end of the URL to ".docx".

Comments and feedback MOST welcome!
Click to expand...
Great guide! Thak you very much for this. My quad has now problems with cooling, I have long been committed to fixing the liquid cooling system. This solved my concerns, I don't need to do water cooling, but a nice, sleek air...
Thank you very much!
 
After doing the "new blood mod" to my quad a couple years ago and then having CPU B overheating to the point of checkstop this has my attention. I'm still not entirely sure what happened since it was running fine for a couple years (almost daily use) with temps maxing out in the 60s and idling in the upper 30s. CPU B gradually started getting warmer until it couldn't get to the desktop.

I have the "version 2" dual pump unit and both pumps still work and the coolant lines coming out of the copper blocks feel warm as usual. Not looking forward to taking it apart to see what went wrong but air cooling it looks like a likely idea i'll eventually do. I take it there's no difference between the CPU cards between the LCU styles?

EDIT: I also used leftover Kryonaut Extreme from a liquid cooled gaming PC I build.
 
First of all, great guide, good job man! :cool:
What i wanted to ask, is there any information about the wire connection for the pump? Like what signal does the motherboard send to the pump and is there any feedback from the pump to the motherboard?
If so, i can design a circuit and a circuit board that can increases the fan speed from the A400 heatsink as the pump speed goes up, eliminating the need for an external fan PWM controller. So it doesn't confuse the G5 fan control unit :D
The principle would be as following:
1. You will have full detailed schematic, pcb, gerber files and part list for the expansion controller board that you can order and buy yourself and assemble it (PCBWay/JLCPCB for the PCB and Mouser for the electronics). The PCB will probably be no larger than 50x50mm.
2. Use the original connector for the G5 pump to plug it into the expansion board.
3. Use original connectors from the fans to plug into the board.

If the DC current from the pump connector is too low, you can always use power from the Molex connector on the DVD, i can also make a connection on the PCB for that option.

If someone has this info, it could be a useful project for the G5 Quad community :D
 
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Interesting idea @NikolaPPC, but I don't think it is necessary. There is no external PWM controller. The A400 fans are wired directly to +12v and run at their full speed all the time, but they are whisper-quiet; I am very sensitive to noise (the noise from the stock Apple fans is what started me working on all of this!) but there is no issue here at all.

I ran a sound meter (dB SPL) about a foot in front of my Air Quad, and it registered anywhere from 30 dB to 32 dB. Various online sources describe this as "whisper", "soft", "quiet", etc.

I would have preferred the sound meter app to measure dBA, which is a more human-nuanced scale, and I finally did find ONE that said it did dBA, but I am not sure I trust it. Nonetheless, it registered 36 dBA one foot in front of my Air Quad. More or less the same adjectives apply ("whisper", etc.).
 
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Well, the idea is there, if people have interest in that :D
It would save up the 1 PCI-E slot and the G5 would use it's fan control unit, for all the fans, like it did with the LCS.
Like a trick module so the quad thinks it has a pump in it :D
It won't be a problem to make it so the fans stay always at a full speed (lowest speed for the pump is the max speed for the fans etc..)
 
Thought about it before. Given that the PWM signaling for the LCS is basically a black box, that's the only roadblock from having such a board made.
 
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Hi All, I have updated the Air Cooling document to v0.2, adding more detail in many places and doing a general clean up of grammar and typos throughout. I have updated the link in the initial post so that it points to the new document, and I have reproduced that link here below for your convenience:

https://inverary.net/LCS/Power Mac G5 Quad Air Cooling, A-Z Guide, v0.2.pdf

If you have already downloaded the document but not read it yet, please replace your older copy with this new one from the above link. Thanks!
 
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mac57mac57 said:
Hi All, I have updated the Air Cooling document to v0.2, adding more detail in many places and doing a general clean up of grammar and typos throughout. I have updated the link in the initial post so that it points to the new document, and I have reproduced that link here below for your convenience:

https://inverary.net/LCS/Power Mac G5 Quad Air Cooling, A-Z Guide, v0.2.pdf

If you have already downloaded the document but not read it yet, please replace your older copy with this new one from the above link. Thanks!
Click to expand...
Thank you!
Please, I have question about 12. Air cooling parts:
in what units are dimensions of 92x92x0.5 copper shims ? It is no millimeters, but what is it?
Bottom size of FROZN A400 heatsink is 38x38 mm so this should be enough. But I need to be sure about exact thickness.
 
OMG! You are absolutely right @sailorMH, the shim dimensions provided are simply wrong! I got so caught up in ensuring that I had 92mm fans that I mistakenly parroted that same dimension for the shim, which is not correct.

The units are mm, but the size is 40x40x0.5, not the originally shown 92x92x0.5!

I have updated the document to reflect this, and re-issued. I have updated the link in the original post to match, and reproduce that link below for your convenience.

https://inverary.net/LCS/Power Mac G5 Quad Air Cooling, A-Z Guide, v0.3.pdf

Thanks @sailorMH for catching this key mistake!
 
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Doq said:
Thought about it before. Given that the PWM signaling for the LCS is basically a black box, that's the only roadblock from having such a board made.
Click to expand...
I have both oscilloscope and logic analyzer, so at some point i can tinker with the I/O signals for the pump. The only downside is that i have 2 Quads with single pump LCS, so i can't guarantee for sure what LCS with dual pumps do..

There are a few possibilities that come to my mind like (maybe even combination of the following):
1) Motherboard measures the power draw of the pump
2) There is a sense resistor on the pump that has some specific resistance, so the motherboard knows if the pump is there or not
3) An integrated chip on the pump sends a signal back to the motherboard

If anyone has more ideas, I'm here to discuss them! :D
 
How are the temps while under load? After rebuilding the LCS in my quad a couple years ago the hottest it got was 64C in Cinebench. It then dropped almost instantly to mid 30's after the test. I was quite impressed at the time... but unfortunately it only lasted about 2 years. CPU B went out of control while CPU A temps remained the same.
 
So far, under the heaviest loads I have thrown at it, 61 C has been the highest temperature I have seen, and like yours, it drops right back into the 30s when the load is removed. Since this is now air cooled, I don't expect that to change over time.

In your case, if CPU A remains cool but CPU B has spun out of control from a temperature perspective, I would suspect debris-based blockage in the CPU B cooling block and microchannels. Unfortunately, you can't fix that without taking the whole cooling loop apart. As I said in my LCS Overhaul guide, even if you do a perfect job with an LCS refresh, it is only temporary... liquid cooling is simply inherently prone to more failures than air cooling.

Air cooling is "forever", at least in my experience. Thermal paste may need to be refreshed every ten years or so, but that is simple enough. My G5 Dual 2.3 GHz, which is air cooled and was purchased in 2006, still runs cool and quiet today, nearly twenty years later. I have never done a thing to it from a maintenance perspective other than blowing out dust from time to time. It is a solid workhorse. 20 years and counting is close enough to "forever" for me!

It is worth noting that this machine runs 24x7x365, hosting the internet-visible HappyMacs Gopher server. It has worked hard most of its life and yet remains 100% thermally stable.

Back to my Air Quad, the results listed above are all from informal testing with real world loads (Photoshop, Carbon Copy Cloner, network-to-disk copies, disk-to-disk copies and so on).
 
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Rebuilding the LCU sounded like a good idea at the time and would keep the machine in a more "traditional" state.

I was thinking about somehow using a D5 pump, small reservoir and 240mm radiator to create some kind of custom cooling loop like a modern PC. It probably could be done but I don't really feel like doing it and the price would be a lot higher than the air method.

Just ordered everything I need. Now it's just a matter of when I get around to it. Hopefully sooner than later. The quad has my entire physical library of music on it.
 
Whoops! Yeah, just Dual, not Octal!

I have edited the offending post and corrected it. Thanks for catching that @Doq. I have been typing "Quad" for so long now in these posts that it just flows naturally off of my fingers!

... but even though it is "just" a Dual, it is a heck of a machine; solid, reliable, fast, and serving Gopher to the world for a very long time. It is my emotional favorite amongst the Macs I have.
 
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amishallin said:
The quad has my entire physical library of music on it.
Click to expand...

This sounds dangerous, @amishallin. Before I did anything with that Quad, I would extract the hard drive from it, put it into another Mac and get a backup of your music, and whatever else is of value on that HDD.

I am suggesting this because you say CPU B is out of control thermally, so I am guessing that the machine will not boot, or if it does, it check stops shortly thereafter. Hence you can't use the Quad to back up the data... you have to get the HDD out and do it externally.

BTW, if the machine runs at all, there may be another way. Boot it to Open Firmware (hold down SHFT+Opt+O+F while you boot) and use an OF command to turn off CPU B. If you can get this far, the machine will boot using just two of the four cores, and you effectively have a "half Quad", or said another way, a 2.5 GHz Dual.

The OF command you need is:

setenv boot-args cpus=2

Enter that followed by the command:

mac-boot

and with any luck your "half Quad" will come right up and run cleanly.

Your data is tied to that HDD, not to the Quad, so get the HDD out and back up everything important on it. Then put it back and carry on. This is important because anytime you work inside a computer, you run the risk of damaging it in one way or another. If that were to happen, you might render your Quad unusable, at least for a time anyway. You will be SO grateful you backed up if that happens!
 
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If need be I could boot my dual CPU Quicksilver G4 from the quad's drive. The music is still on physical CDs if for some unforeseen reason the drive dies... but i'm pretty sure it'll boot right up when I do the air conversion. It also has a bootable installation of Adelie Linux (separate drive) to boot from and check stability.

Yes the machine checkstops during boot. However, it did the same thing before I rebuilt the LCU.
 
mac57mac57 said:
BTW, if the machine runs at all, there may be another way. Boot it to Open Firmware (hold down SHFT+Opt+O+F while you boot) and use an OF command to turn off CPU B. If you can get this far, the machine will boot using just two of the four cores, and you effectively have a "half Quad", or said another way, a 2.5 GHz Dual.
Click to expand...
If the Quad can boot to Open Firmware, then it can boot to FireWire target disk mode, and you can copy files off of the HD to another Mac using that (but it maybe won't be as fast as removing the drive and copying the files directly).
 
Got all the music backed up on my G4.

I removed the LCU today and found some dark gunk in the inlet/outlet of the CPU A (top CPU) water block. The mass moves when the unit is rocked back and forward. Was almost positive it was CPU B. Some images are attached.

I'll start the actual mod tomorrow.
 

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@amishallin, is this a dual pump LCS? Neither of the single pump LCS' I have worked on look like what your photos show.

Nonetheless, since the air conversion doesn't depend on the pre-existing LCS, the conversion should still work fine
 
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