Air Cooling a Late 2005 G5 Quad

[mac57mac57]

Regular readers of the MacRumors' PowerPC forum will know that I have struggled mightily over the last two plus months to overhaul the failing LCS of a conventional Power Mac G5 Quad. I have been mostly successful: CPU temps are now wonderfully controlled (CPU A idles in the high 30s, CPU B idles in the low 40s) but fan speeds are still higher than I wanted, now idling in the 2800 RPM range. This still creates enough noise that the machine is not tenable (to me at least) for routine work.

Getting to this point has taken both an enormous amount of work and an enormous amount of frustration as I battled a nearly continual series of leaks that I had to hunt down and seal up. In addition, I had to tear the machine down to its most elemental pieces to get the Liquid Cooling System (LCS) back to the point where it would accomplish adequate cooling. It was highly detailed, incredibly finicky and very error prone work... and when I was done, while CPU temps are now great, fan speeds are still not, and honestly I have no hope of ever correcting that; my last gasp plan is to replace all the stock Apple CPU intake and exit fans with super quiet ones and hope that the high fan revs will no longer be an auditory issue.

HOWEVER, I started with two Quads that had failing LCS units and after the experience of the first one I have no intention of attempting an LCS overhaul on the second one. I have had it with liquid cooling... too darn finicky and unpredictable. So what is the plan for the second Quad? Air Cooling!

I will be building on the excellent work that @Doq has done and documented - see his thread:

Because I Can: Air-modding a Quad With... PC Coolers!?

I plan to attempt pretty much the same modification that he has, hopefully with similarly successful results.

As I start, here is the Quad to be modified into an "Air Quad", with the LCS/CPU assembly extracted from the machine and torn down to its elemental parts:

Here is a shot of the five new parts needed to accomplish the air cooling modification (two coolers, two copper shims and one tube of thermal paste, almost identically the parts recommended by @Doq):

The FROZN units are PC (yes, PC) air coolers and will replace the LCS. The copper shims (the small blue box in the center contains 4 such shims - I will only need two) will be used as intermediaries between the CPU chips and the FROZN A400 coolers. Finally, the Kryonaut Extreme thermal paste will mate the CPUs to the shims, and the shims to the coolers. Kryonaut Extreme is the most highly rated thermal paste I could find (thermal rating of 14.2 W/mK) but it is noted for being difficult to spread, so it may be an issue yet.

I purchased the two FROZN units on eBay, while the copper shims and the Kryonaut Extreme thermal paste were purchased at Amazon.com. I had to buy the FROZN units on eBay because they do not appear to be for sale new anymore, except for "new old stock" on eBay, having been replaced with the larger (120mm) FROZN A410. Two of these will not fit into a Quad - each one must be a maximum of 92mm to fit.

So here we go again. Like my LCS overhaul, I plan to photograph everything extensively as I go, and when done write a full blown, highly detailed and heavily illustrated guide to accomplishing air cooling of a Late 2005 Power Mac G5 Quad, so that others can replicate this result simply by following a detailed set of step-by-step instructions.

In this effort, I have to thank @Doq once more - his post/guide points the way, provided me with enough critical information to feel confident in trying this modification. Lets hope that this effort yields both cool CPUs and quiet fans. We shall see!

 

[joevt]

Regarding the copper shims, https://forums.macrumors.com/thread...-a-quad-with-pc-coolers.2427612/post-33168681 says the CPUs will thermal stop without them.

The post at https://forums.macrumors.com/thread...-a-quad-with-pc-coolers.2427612/post-33863463 says the shims might not be necessary depending on the cooler. Specifically, if the cooler has a solid copper plate then the shim is probably not necessary.

Do the FROZN A400 not have a solid copper plate? What does the bottom of those look like?

 

[ADunsmuir]

The FROZN A400 were still available on Amazon.ca this afternoon, at $C39 with free shipping. This was significantly less than current units available on eBay.ca so I ordered 2 just in case radical surgery on my Quad should become necessary in the future.

 

[Doq]

Do the FROZN A400 not have a solid copper plate? What does the bottom of those look like?

The bottom is the exposed heatpipes surrounded by aluminium. The die is too small to contact all of the heatpipes at once, thus requiring the shim.

It's best practice to use a shim regardless when working with direct-die cooling but I understand also that it may not be strictly required if the contact point is solid.

The FROZN A400 were still available on Amazon.ca this afternoon, at $C39 with free shipping.

I just checked and A400s are also still available on Amazon US (and on sale a bit).

 

[joevt]

The bottom is the exposed heatpipes surrounded by aluminium. The die is too small to contact all of the heatpipes at once, thus requiring the shim.

It's best practice to use a shim regardless when working with direct-die cooling but I understand also that it may not be strictly required if the contact point is solid.

Oh, right. That makes sense. AMD and Intel CPUs usually have their die covered by a heat spreader. This is the function of the copper shim for the PowerPC CPU.

 

[mac57mac57]

Interesting. When I type this in to Amazon.com, I get pages and pages of A410's! I'll try again.

 

[mac57mac57]

... this time, I got ONE A400 entry, priced at $24.99! The rest were all A410 or higher.

Darn! I paid nearly $40 each for the two A400's I purchased on eBay! 😕

 

[jktwice]

We’ve seen air cooled quads happen using modified 2.3GHz coolers, but obviously this is not sustainable.

Hopefully your efforts here bear fruit because then the rest of us Quad owners can keep these machines alive and happy for just a bit longer.

 

[mac57mac57]

Thanks @jktwice. I hope so too!

We know that it CAN be done - @Doq has already done it. The question is whether it is a repeatable procedure and whether I can document it in such a way that anyone with PowerPC Mac skills can accomplish it themselves.

The effort is well worth it. Equipped with Sorbet Leopard and the latest Aquafox browser, these machines are still fully functional in today's world. They can surf the web, handle today's web-heavy emails, do your banking, balance your budget, edit photos and videos, etc. Apple released an incredible beast of a machine in the G5 Quad. 20 years later, it is still a viable machine.

 

[mac57mac57]

@Doq, in your work to air cool a Quad, do the copper shims sit directly on top of the CPU? I would assume they do, but that would place the edges of the shim in contact with a whole variety of components directly around the CPU. Granted, these are the cases of the components, not their electrical connections.

I was thinking of cutting out a shaped-for-the-purpose piece of thin non conductive material and placing that around the CPU chip just to be safe, with the entire surface of the chip exposed, but the rest of the area under the shim "insulated" with this material. Even paper should work, since its ignition point is above 200 C.

At any rate, I just wanted to check whether you took any precautions to ensure that no electrical contact occurred - copper is very conductive after all.

Thoughts?

 

[mac57mac57]

Today was not a "do the air cool work" day. It was a "figure out the mechanical alignment and connection procedures" day.

To that end, a few photos. First, here are all the parts that come in the A400 box:

There is the unit itself, its fan (provided in a separate box-wthin-the-box), and a whole box of mounting hardware, split between the left and the right of the photo above, which supports both Intel and AMD processors and motherboards. The Intel-oriented hardware seems the right fit for the G5 Quad.

Also included in the A400 box is a tube of pretty darn good thermal paste - 10.5 W/mK! I will stick with my Kryonaut Extreme, which is rated at 14.2 W/mK, but it is nice to have a fallback if needed. Both tubes are relatively small. If, like the LCS overhaul, this needs to be disassembled, fixed and reassembled a few times, having extra thermal paste on hand will be helpful.

Next, here is a photo of what the underside of the A400 looks like. Once you see this, it is clear why the copper shims are needed. They overcome the facts that (a) the copper on the underside of the A400 is not continuous, and (b) the cooling surface of the A400 is significantly larger that the 970MP chip surface. The shims overcome both. The part of the shim in contact with the CPU face picks up heat from it, then effectively spreads that heat over the larger surface area of the shim, from which the full cooling surface of the A400 can extract it.

I have placed a shim directly underneath the underside of the A400 in the photo below:

The fan must be attached to the A400 after it has been mounted and screwed down. A set of "fan clips" are provided to accomplish the attachment. The photo below shows how they are used to connect these two parts - this does require a little bit of mechanical pressure to stretch the fan clips down to fit into the slots on the sides of the A400:

By the way, which side of the fan faces out is a pure guess, based on the very small photo provided with the instruction manual.

Finally, this is a photo of the required alignment of the CPU card, the copper shim, the mounting hardware, and the A400:

The final photo below shows how the A400 will fit down onto the mounting hardware, allowing it to be screwed into place, once the mounting hardware (which is just sitting on the CPU card in this photo) is itself screwed down:

I am missing some non-conductive washers to build up a small gap between the CPU card and the mounting hardware piece closest to the CPU card's existing radiator, and so that is all I can accomplish today. Once I get these washers, more progress can occur. I actually don't see this initial assembly taking too long, as I look at how everything fits together. This will not be like putting together a few Lego bricks, but it looks SO much simpler than an LCS overhaul!!

 

[Doq]

@Doq, in your work to air cool a Quad, do the copper shims sit directly on top of the CPU? I would assume they do, but that would place the edges of the shim in contact with a whole variety of components directly around the CPU. Granted, these are the cases of the components, not their electrical connections.

Yes, but the CPU die clears the surrounding components (it'd have to to accommodate the stock coolers, which were also copper, and have big ol' plates around it).

The fan must be attached to the A400 after it has been mounted and screwed down. A set of "fan clips" are provided to accomplish the attachment. The photo below shows how they are used to connect these two parts - this does require a little bit of mechanical pressure to stretch the fan clips down to fit into the slots on the sides of the A400:

Watch out. There's not enough width clearance for the inside clips to attach the fans without introducing stress to the processor cards and reducing cooling enough to produce a checkstop. This is why I had the center twist ties originally and later the 3D print. The outside clips still work though.

In order to make this work, you'll need to assemble and install both processor cards simultaneously as a single unit (much like with the stock cooler, but way more fiddly as it's not fully attached on all sides.

Now that I think about it, you could probably get away with using both clips by installing one of the coolers in reverse (staggered configuration), though I don't remember offhandedly if you can install the fan on either side.

By the way, which side of the fan faces out is a pure guess, based on the very small photo provided with the instruction manual.

Generally, the side with the logo is the direction that air flows from, with the power rating sticker on the reverse for the direction air flows to.

I am missing some non-conductive washers to build up a small gap between the CPU card and the mounting hardware piece closest to the CPU card's existing radiator, and so that is all I can accomplish today.

I knew this was going to happen and I was going to point it out but you beat me to it.

I do notice that some of the stock pieces are also not shown. I'm interested to see what your solution for that will be if you go with something different in that regard.