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Doq

macrumors 6502a
Original poster
Dec 8, 2019
672
911
The Lab DX
So, I recently happened upon a Quad. However, the LCS was sad; the system was checkstopping mere seconds after power-on.

I noticed it wasn't leaking, so it was a good candidate for the New Blood Mod; however, I couldn't care less about the stock LCS, and I've heard horror stories about actually flushing the pumps, so I 86'd the LCS real quick. That left me with either air-modding it or rolling a custom liquid cooler. I wasn't particularly keen on the cut-required modifications to 2.3 coolers to make them fit, so I thought:

"PC cooling has come a long way since 2005, what if I just used a couple of those?"

So I did. And oh boy, was it a struggle.

First, I had to find coolers that would actually fit. After taking measurements, I determined that you want 92mm coolers, two of them. 92mm will fit perfectly side-by-side for the dual G5s. Anything bigger and they won't fit in the chassis, and anything smaller is probably not going to provide enough cooling capacity. Speaking of cooling capacity, as the PC world has all but adopted 120mm coolers as the de facto standard, finding 92mm tower coolers are quite difficult. After a bit of perusing, I went with the ID-Cooling FROZN A400 (idcooling.com), as it provided the right size and a fantastic thermal rating for its size. It claims 180W of cooling capacity, which is (probably?) more than one of these 970MPs can kick out.

Mounting it was... actually rather easy, though I hope you don't mind logic board modifications and throwing out the remainder of the stock mounting hardware to make it happen.
20240521_152356_HDR.jpg

The holes circled here just so happen to perfectly (enough) fit the Intel mounting hardware that comes with the FROZNs. You'll need (for each CPU):
20240611_135441_HDR.jpg
- The FROZNs Intel mount hardware (just the metal bits)
- The spring screws that mount the G5s to the original cooler. Toss the buckets but keep the spring and screw.
- The thumb nuts included with the FROZNs
- 40mm x 40mm x 0.5mm or 1mm copper shims-- the CPUs will thermal stop without them.
- Two 1mm-1.5mm thick plastic or rubber washers. The ones I used came with a hard drive tower kit I picked up. I believe you want the centre hole to be about 3.5mm (the size of the screw). These are used to balance out the cooler mount-- without them the pair of screws closer to the edge of the processor card would be higher than the two closer to the middle.
20240611_135613_HDR.jpg

20240611_140002_HDR.jpg
Install the mount hardware using the spring screws and the thumb nuts, making sure to use the washers on the edge screws for balance. Attach copper shim(s) to heatsink with a small amount of thermal paste. Paste the CPU, attach cooler to processor card. A finished cooler should look like this:
20240611_140809_HDR.jpg

Of course, there's a little bit of jank involved. You won't be able to use the fan clips as intended-- they make the coolers just a bit too wide and the CPUs will checkstop. Instead, use only one of the clips for each cooler, attached to the edge away from the opposite cooler. Then, link the two fans together using a twist-tie or a paper clip.

You will also need to modify the logic board; the two holes we used for the mounting hardware was previously used by the alignment posts in the chassis. They will need to be removed. You might be able to remove them without removing the logic board, but I wasn't able to do this.
20240611_141713_HDR.jpg

Install complete processor unit into logic board.

In regards to the fan situation, since the original LCS was tossed, we can cut and reuse the pump power cable to power the fans. Pins 1, 2, 7, and 8 are 12V, 12V, Ground and Ground respectively. Soldering headers to these cables allow us to power the fans using the original cable, without having to source power elsewhere. I didn't bother with PWM control; apparently G5s use funny PWM signals anyway and would likely confuse the fans. The fans will run at max whack at all times, but I didn't see this as an issue. Plug in the fans to the newly created headers and send it.

I wish I had more pictures, but it was a lot of frustration that I just wanted to be done and over with it.

Haven't done stress testing yet on it (I was too overjoyed to see it work at all so I don't quite know if this is sustainable long-term but given the thermal capacity and it idling at 37 C/38 C I don't see why it wouldn't work under load.
20240528_151904_HDR.jpg
20240528_152002.jpg




Update: I ran Geekbench a couple times and saw one of the cores (B2) peak at 95 C. But it didn't thermal die, so I'm calling it a win!
 
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Sure thing. I sent the de facto "easy" CPU stress (yes > /dev/null) at it to see how well it fares and....

One instance got about 63/65 C
Two instances topped out at about 75/74 C
Three instances saw a peak of 94 C on the B2 core but settled down closer to 79-81 C
Finally, a full send with all four instances really spun the fans and actually resulted in lower temps of 77/78 C, with some peaks in the 80s or 93-94 on that pesky B2 core.

I left the full send running for the length of a couple of (real) YouTube videos (about 20 minutes) and it stayed at that four instance result, no thermal death here as well. The B2 core is a little concerning, but also my main workstation peaks at 95 C under stress as well, so as long as it's not at T-junction it's probably fine. I actually got spooked when the screen turned off but it was actually just the idle timer.

This test probably also cost me like $10 in power usage alone. Hyperbole, of course, but I do want to get a kill-a-watt to see real power usage as well.
 
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That's quite impressive. My quad likes core B2 also. Not sure why but sounds like it may be normal.

You must've seen my images in the new blood mod thread. I had a lot of "fun" with that... but at least it works now.
 
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I sourced some 40x40mm copper shims to redo the mod and while I was there I also got a few pictures of the actual process, which I have added to the OP.

Thermal results are basically identical, but as always YMMV.

Also, in regards to power, my G5 is only sucking down 450W on full stress, which isn't nothing, but also probably doesn't justify the use of a C19 power connector on the supply, even if it's rated for 12A.
 
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I sourced some 40x40mm copper shims to redo the mod and while I was there I also got a few pictures of the actual process, which I have added to the OP.

Thermal results are basically identical, but as always YMMV.

Also, in regards to power, my G5 is only sucking down 450W on full stress, which isn't nothing, but also probably doesn't justify the use of a C19 power connector on the supply, even if it's rated for 12A.

Very nice setup. Considering that the original fans already blow air to the heatsink, have you considered not installing the CPU fans?
 
Very nice setup. Considering that the original fans already blow air to the heatsink, have you considered not installing the CPU fans?
I have. It thermal died instantly.

I figure it's probably either because the case fans don't spin up quick enough or the sinks themselves aren't capable of handling the thermal capacity without the fans. It may be possible with a physically larger sink (a la the 2.3 heatsink conversion mod) but I'm not sure if there are any that would work in this instance without heavy modifications.

The CPU fans are running full tilt at all times anyway (as G5 pump PWM signals are funny, I didn't connect them) so they may actually be what's keeping the thermals in check.
 
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The PC Cooler Quad is still running great. This is a bit of an extra optional piece that I made to make fan mounting a little easier.

This is a very small 3D model that interlocks the two fans using the inside mount holes, making the mount cleaner and less janky overall. Print two for best results.

quadfanlink.png
 

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@Doq, this sounds REALLY interesting, and a great result as well. Well done!

Where did you get the copper shims from? That sounds like the only part that would be difficult to acquire.

One other question... with the CPU fans running full speed all the time, how noisy is the system when running? There are multiple sound level measurement apps for smart phones these days. Did you try any and get a dB rating of the noise level?

In the end, my Quads both worked fine; they were just too noisy to use comfortably because the fans were running at full speed. If I go to all the work to create an air cooled "FrankenQuad" and end up with a different set of fans still running full tilt and making a devil of a racket, I won't have solved the original problem!
 
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Where did you get the copper shims from? That sounds like the only part that would be difficult to acquire.
I just bought a pack on Amazon. They were "Easycargo" branded and in a pack of 4 of 40x40x0.5mm. You'll only need two of them, one for each sink. You don't have to get the specific one that I did but as long as they are at least 40x40x0.5mm you should be good.

One other question... with the CPU fans running full speed all the time, how noisy is the system when running? There are multiple sound level measurement apps for smart phones these days. Did you try any and get a dB rating of the noise level?
It is audible, though I personally wouldn't mind it. At my distance (which has the machine directly in front of me) it sits around 20-22 dBA or so, and moving the recorder directly behind the exhaust nets 30-31 dBA. Ambient noise level here is 15 dBA, so not bad on either front.

During my stress testing the stock case fans were louder.

You could probably source some Noctua fans for even less noise.
 
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@Doq, I am about to embark on the same project... converting a G5 Quad with a troublesome LCS to air cooling. Reading through your thread on this topic, I don't understand one thing... where do you place the copper shims? Presumably they are thermal pasted right onto the CPU chips, and then the coolers sit on top of that?

One other question. It appears that you have left the original Apple CPU intake and exit fans in place, and they run at full tilt. Isn't the finished product therefore still extremely noisy? You quote 20-22 dBa, but those original Apple fans are much louder than that aren't they?
 
Correct. Though I usually paste the shims to the coolers first, then pasting the entire unit to the processor afterward. Depending on which coolers you have the shims might not be necessary. If your cooler has a solid copper plate already (rather than exposed pins) you can likely skip the shim step.

My stock fans do not run at 100%; only the additional fans on the coolers do.
 
Thanks @Doq. I have ordered all the parts today - 2 of the FROZN-A400 coolers, the copper shims and new thermal paste (Grizzly Kryonaut). When it all arrives, let the "fun" begin!
 
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@joevt, it just might. The dimensions look promising. I would be a bit worried about is overall width, and it is 50% more expensive than the FROZN units that I have ordered.

Still, air cooling a Quad is a huge leap onto the wild side, and nothing is guaranteed to work. I may yet find that I need a different part. I have saved your a link to the Noctua unit in your note on my Amazon Wish List... I'll let you know if I go that way.

Thanks for the pointer.
 
It probably can, though the tolerances would likely be tighter than they already are. Some (more) creativity might be required to attach the cooler fans, for instance.
 
Another thing that might be interesting is using all in one liquid coolers. I don't know what size one would try. For the dual CPU G5 Quad, maybe have one connected to the front and another connected to the rear.
 
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The Kryonaut Extreme has been delivered, and the copper shims are out for delivery today. The FROZN units are still a few days away from delivery, but I can't wait. I am really eager to get going on this conversion - it should be so much better than the LCS work I have been embroiled in for (literally) months.
 
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Well darn, the Kryonaut Extreme and the FROZN units have been delivered, as were the copper shims... except that they didn't send me the 4 copper shims I ordered; instead they sent me ONE full copper heatsink, which I absolutely cannot use. :mad:

I kicked off the return/replacement cycle to get what I ACTUALLY ordered, but now I have to wait until next Thursday to get them, so the air cooled mid of my Quad is on hold until then. Darn! :rolleyes:
 
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