Fully Internal Watercooled SLI system DIY project

I wondered why the most recent thing I could find was the Asetek M18x prototype from 2013 so I made one myself to investigate whether fully watercooled was feasible going forwards.


Preliminary testing:
CPU + GPU temperatures exceptional
Stock fans/rads not sufficient to keep loop temperatures acceptable.
This was something I was expecting since the P370EM has weak fans and small rads, and ran hot on its stock cooling even for the lower power hardware of its era (55W max TDP CPU, 65/75W GPUs) and had plans for.

GPU/CPU temperatures themselves are fantastically low though. About 10C over loop temp. CPU maxed at about 70C. Highest GPU temp I've seen so far at 115W is 65C.

But the loop heats up beyond >40C which is getting concerningly close to the 60C softening point of the cheap PVC tubing. (I have some more temp resistant ~200C silicone tubing en route)

With the external fans on and the 240mm rad cooling as well, loop temps stay acceptable <10C dT over ambient and the CPU sub 70C, GPUs ~60C.

The 3940XM somehow managed to drop dead during fitting and testing so the maximum CPU load from the 3720QM @ 3.8ghz is 65W so far which it handled at 70C

Fan control is through the RLECViewer fan control app - it is purely based on temperature for now in 5C gradients, which is good enough for now (although it does kill Fn+9 max fans functionality). In a perfect world it would be nice if the Obsidian fan control would work with the P370EM, its combination of load based and temp based schemes would be ideal.


Current status:
Connected to external pump/res (and optional 240mm rad)


TODO:
mod and add pump to ODD bay + wiring (slimline sata connector 5V -> boost converter -> pump 6V-12V)
fab and add res with bleed+fill port upstream of pump
redo GPU2 vrm/memory heatsink with right angle facing the other way for the line into HDD bay area
mod the case to fit the tube back to the ODD bay area going between RAM1/RAM2/msata and battery frame area
add 5V fan+rad+wiring to HDD bay (wiring: DC and ground lines spliced from GPU2 fan header)
add 5V fan+rad+wiring to ODD bay (wiring: DC and ground lines spliced from GPU1 fan header)
replace/tweak fan control of GPU1 fan? sounding a tad whiny/dodgy/occasional non-spin-up at low RPMs
System BIOS flash to the P370EM3 version and/or GPU VBIOS roulette to enable updates of 2+ year old drivers while retaining all display outs!!!
figure out how to route the external loop section via the detachable quick disconnects. Probably will have the inlet going into the CPU and the outlet after the slave GPU. That shouldn't cause too much of an issue with opposing flows from the dual pump/spliced lines.
replace PVC tubing with silicone (higher heat tolerance)

 

leak testing: post-double-45-U join soldering but pre-final assembly low temp/heat plate soldering

part way through the long and tortuous alignment process


Schematic of what is currently installed (except for pump/res):


Current final plan (except for the external-in to CPU heatplate, crossing that over the GPU1 heatsink is a no go):

 

Some testing.

Furmarking at ~250W load (2x115W GPU + part load CPU)
The temps below are after about 1/2 hour allowing the temperature to reach equilibrium
Loop temperature stabilised at a very toasty 50.6C which represented a delta T of approx 25C to ambient
The waterblocks themselves are working well, delta T of about 15-20C on the CPU and 10-15C on the GPUs (compared to loop temp)
Some throttling started on the GPUs which I wonder if it was the VRMs and the old thermal pads on them, combined with the plates getting toasty (GPU2 memory/VRM heatsink is literally the hottest point in the loop after all the heat generating bits)

This is absolute worst case scenario but still compares well with the stock results with both the 1070s at 115W, of low 80s master and high 80s slave.
The two additional fans and rads I'm planning should keep that loop temp down further.



This is after reaching that 50.6C high point, I connected the fans (1200rpm silent fans in push/pull so not that great) on the external 240mm radiator which brought the temps down to mid 30s over a couple minutes. The "70%" fan speed the laptop fans dropped to at this point is fairly quiet. I have the minimums set at "35%" in the fan control app which is almost inaudible.



There's a bit of a delta T between core 0 and core 1 on this CPU (not shown in the screenshots). Something I remember observing in the P170EM as soon as I liquid metalled this particular CPU. At times it's as much as 10-12C. Alternatively, perhaps it's because there's no fill in the gap under where the copper pipes are soldered to the heatplate (the low temp solder is very thin and flow-y). In any case I will redo the CPU heatplate at some point to incorporate the external quick disconnect line-in.

I tried to play whatever I could find on the data drive - Doom 2016 managed to run without steam even being installed (???!) - but it was rubber banding between 30fps and 70fps quite badly under DX11 SLI, damn these old drivers from 2016

 

I love this project. I featured it in the latest Forum Spotlight.

Great work!

Charles

 

Thanks. Haven't had a lot of spare time for progress of late but have done the wiring and fitment of the pump and everything in the ODD bay which required a bit of case grinding to make the space

 

Nice mod! I'm looking forward to see the final result

 

Awesome mod

 

So am I! I just came home after a week of holiday. Cramming everything into the ODD bay took a lot of time and a few different attempts at sealing to get it watertight.

Cheers

 

The water finally flows.

However during assembly and leak testing I've broken one of the seals I made causing a pinhole leak near the intake to the pump. Even though its so small I could probably deal with it coating the outside with liquid electrical tape I am being perfectionist with leaks, before I fasten everything with cableties.

I misordered the silicone tube, it is only 1mm wall and is too flexible and kink prone. Bummer. $20 wasted unless I spend time wrapping it in tape or something.

Pump works just fine on 5 volts even though it's spec is "6-12V", small bubbles take about 20 seconds to do a full loop which is sufficient flow. I've still got the boost converter in between the 5V source from the slimline Sata with the potentiometer screw accessible so I can turn it up should it be needed. That's all wired with 3 pin connectors which is how I can run the pump like this with an external power supply.

In hindsight I should have just got a sheet of 1mm or 2mm acrylic and cut and shaped it to fit.

 

Ugh. Looks like the EC panics on POST with the pump drawing from the 5V pins from the slimline SATA on boot. Upon pressing the power button, the pump fires up, but that's it, no display, and after about 20 seconds the fans go to max and the Capslock and Scroll lock LEDs start flashing. Disconnect the pump = boot as normal

Pump itself shouldn't be breaking anything, while it's rated for 0.35A at 12V I can't see it drawing more than 1A at 5V given how much slower the rpms are

I may have to integrate a switch, or get the 5V from elsewhere (like USB), or figure out how the enable pin in the slimline SATA connector needs to be altered (I think I read somewhere for the specification it's a 1Kohm resistor to ground, but will have to try and remember where I saw that.)