Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Doq

macrumors 6502
Original poster
Dec 8, 2019
480
729
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 96mm coolers, two of them. 96mm 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 96mm 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!
 
Last edited:

Doq

macrumors 6502
Original poster
Dec 8, 2019
480
729
The Lab DX
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.
 
  • Like
Reactions: repairedCheese

amishallin

macrumors member
May 31, 2020
85
60
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.
 
  • Like
Reactions: Doq

Doq

macrumors 6502
Original poster
Dec 8, 2019
480
729
The Lab DX
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.
 
Last edited:

ftalbot

macrumors member
Nov 25, 2012
47
28
Québec City
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?
 

Doq

macrumors 6502
Original poster
Dec 8, 2019
480
729
The Lab DX
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.
 
  • Like
Reactions: ftalbot
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.