Prototype Oki-Doki : a GPU bifurcation and watercooling dedicated case, from 9 to 14L


King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016
Hi there,

I've been working on a compact GPU-based rendering workstation project for the last 18 months.

Since two GPUs are enough what I need to do, I decided from the start to base my design around a Mini-ITX motherboard supporting bifurcation, wihch allows splitting a 16X PCIe slot into two 8X slots with a proper bifurcated riser.

At the very heart of the project, this custom dual-slot bifurcated riser made by C_Payne from [H] : the only custom piece of this project !


The enclosure should be kept the most compact possible, while respecting the following specifications :

  • Standard hardware as much as possible.
  • House two dual-slot GPUs of virtually any length.
  • Hardware to be watercooled.
  • Only one PCB riser - no ribbon, only one PCIe connection : reliable and PCIe Gen.4 compliant.
  • Easy to maintain : open volumes.
  • As silent as possible : as much rad space as possible wit 5V fans.
  • Inexpensive to produce : flaptack design, no bends.


  • Two 240 slim radiators with 25 mm fans @ 5V.

  • 6.4/9.6 mm (1/4 ID) Koolance fittings

Asrock Z170 Fatal1ty ITX
i7 6700K cooled by an EK Annihilator waterblock
2 x 8 Gb Corsair LPX 2400
2 x KFA² GTX 1070 Katana cooled by EK Thermosphere waterblocks
Corsair SF600
4 x 120mm Scythe Slipstream 1200 @ 5V
2 x Magicool Slim 240 radiators



  • Dimension base unit: (H x W x D) 199 X 294 X 248 mm.

  • Volume base unit: 14.5 L.

  • Material: 2 mm anodized Aluminium.

  • Mainboard: ITX supporting bifurcation.

  • Graphics card: 2 slots, up to 285 mm length.

  • Power supply: SFX. Optional Meanwell PSU powering the second GPU.

  • Hard drives: 3.5 and/or 2.5 inch.


Based on all the considerations above, I chose to design a case based on flat aluminium panels, held together using various cube standoffs and L-shaped mounting angles.

Two 240 mm radiators are placed at the back of the motherboard, while both GPUs are placed on top of the motherboard.

Panels drawn in Autocad, then imported into Sketchup.
The central perforated panel will support both the motherboard and GPUs.

Tube routing study made in Rhino, using the great Arcblend command, then imported back into Sketchup

There is room for an extra Meanwell PSU if the SF600 gets too loud.

V1 : 14.5L

V2 : 11.9L

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King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016

Some pictures of the building process.

Understated EK Annihilator block. 1/4 ID Koolance fittings.

The 24-Pin cable has been "cut" in half to maximize GPU clearance.

I made a whole new wire harness from Scratch, using Alphawire Eco-wire line : very thin and quite stiff, which makes them quite difficult to work with at the beginning.
The result is worh the hassle though !

The green PCB is a 12V/5V fan hub.

4 vibration dumpers used to attach the pump to the intermediate panel.
1/4 ID Koolance fittings used for clearance issues.

Two 1070 with their EK Thermosphere block connected through an EK FC-Terminal Dual slot.
Very compact and sturdy unit !
Home-made custom VRM heatsinks.

There is around 6 mm clearance over the pump allowing large GPUs to be used.
The EK SBAY pump is fixed to the intermediate panels thanks to an aluminium piece and four rubber mounts.

Fat sandwich.
The heat dumped by the two Magicool 240 radiators is evacuated from the case thanks to natural convection.
Two slim 120 mm can be mounted on the front panel to help.

Four mounting holes allow me to fasten the riser to the case using 10 mm standoffs.
Makes for a clean and very sturdy result.

I used this low profile extension I had lying around as the fitting was preventing me to simply plug the 8-Pin cables into the GPU.
The empty space above the pump is meant to can welcome an extra Meanwell PSU if needed.

The case can be used either vertically or horizontally.
Having GPUs over the motherboard allow for a clean IO layout, with well aligned blocks !
The way I like it :)

Too many ventilation patterns but I'll fix that soon enough.
My goal was to make this first prototype as cheap as possible.
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King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016
Soooo, any chance you're selling those PCIe risers?

Ahah I have indeed an extra riser (I had two of them made) but I think I'll keep it for now.
One of a kind piece of hardware :)

However, since you have C_Payne contact, you could propose him to join the SFFLAB co-op and make some of his risers more widely available.
He's now challenging himself with lead-free solder which makes his risers ROHS compliant !

Very nice idea!

Waiting for those temps....

I just made quick tests with the four Slipstream fans running at 5V (720RPM) and DDC pump running at 60% max.
The system is inaudible at less than one meter.

Ambiant temp is around 20°.

- 30 min OCCT on the CPU alone : temps stabilize around 63°
- 30 min OCCT on the CPU + Octane bench (rendering) on both 1070 : CPU around 80° (hottest core), GPU 1 stable at 66°, GPU 2 stable at 58°.

IDLE system consumption : 45W
LOAD system consumption (both GPUs and CPU) : ~ 330-340W

CPU Vcore is 1.232V @4.2 Ghz, which isn't too bad for a 6700K. Leaves some room for undervolting.

I'll try to do some more thorough testings later on.
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King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016
Did a quick and dirty render of the definitive panels :

- intake above the GPU,
- exhaust above mobo.

What do you think, airflow-wise ?

They changed the whole Octane for Sketchup plugin interface ; need to get my head around it...
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King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016
Thanks !

The case inner depth is 244 mm : unfortunately too small for a M-ATX board.
However, if I were to increase the depth by few mm, yes you would be able to move the PSU to the back, flip it and have a M-ATX board.

As you know pretty well, if your mini-ITX board supports bifurcation, you don't need M-ATX ;)

BTW, I measured the total system power consumption with a Zalman ZM-FMC2 :

- IDLE : 45W
- LOAD (OCCT + Octane bench on both GPUs) : 340W

Not bad, I could almost get away with the Corsair SF450 PSU, as my SF600 is emitting all kind of electrical noise at idle...

The SF600 also gets quite hot at load because of the heat radiators dump into the case
I'm going to reproduce some panels and flip the radiators, to use the four fans as exhaust.
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SFF Guru
Jun 22, 2015
I thought that the rad intakes dumping heat inside the case onto the mobo was questionable. I have every confidence you'll sort that out, though.


King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016
I thought that the rad intakes dumping heat inside the case onto the mobo was questionable. I have every confidence you'll sort that out, though.

I designed the first prototype horizontaly placed. It works way better vertically though, except for the hot air exhaust by natural convection.
I'll switch the rad fans to exhaust air and will add two intake 120 mm as I have room for them :)

It`s appearance like a lovely microwave oven. lol BTW this pcie riser card maybe only some Special type MB could use. I suggest that you should make a support list which type MB could be launched. It`s helpful.

The riser actually supports any M-ITX board.

The limitation comes from the CPU waterblock compatibility.
The available height between the lower GPU PCB and motherboard PCB is 48 mm, which translates into a ~ 37 mm waterblock max. height, including fittings.

It leaves you with two WB options :

- Safest bet: EK Annihilator.
- More risky : a very low profile block, like the Koolance CPU-390, used with Koolance 6.4/10 90° fittings or Koolance low profile elbow fitting.

I'd buy one of these if you can make some more.

You mean the riser or the case ?
If there is enough interest, I could ask the designer to have a small batch produced in China (right now he's soldering every one of them by hand).
We would have to upfront the money though.


King of Cable Management
Original poster
Piccolo PC
Feb 16, 2016
UPDATE : time to downsize !

The build is working great so far but the case is a bit too large for my taste.
I did not mention it in the first post but this build was never supposed to be 14.5L !

First design total volume was 10.5L.
To achieve such a volume, I based my design around two key elements :

- Use two single slot GPUs -> failure.
The company that prototyped the waterblocks for my 1070 Katana never achieved to make them truly single slot. After two failed protoypes, we decided to stop it there.

- Replace the usual SFX PSU by a G-Unique / Meanwell and custom GPU load switch combo - > failure.
Apparently, the G-Unique/ Meanwell combo is not compatible with my load switch. The load switch would not turn off upon system shut down.
Hereafter a picture of the first prototype.

Anyway, after this short historical background, let's move on to the third version of this build !

Some good news regarding my two previous failures :

- Bykski launched waterblocks for my KFA² 1070 katana beginning of March ! They are not single slot but they are full cover. Which really matters in a small volume with low airflow.
I contacted them directly and they sold my two of these blocks for $48 a piece !
I received them few days later and they are of great quality :)

- I just tried the 24V equivalent of my G-Unique combo : HDPLEX + Dynamo 360 + Meanwell RPS-400-24.
It's working beautifully according to a brief test !
One old HDPLEX 250 rev. 1.3b to power the system, one Dynamo 360 to power btoh GPUs, pump and fans.

@Kmpkt : I wish I could use your Dynamo mini instead of the HDPLEX 250 but the PCB is too high by ... 1 mm.
I do not want to damage the components at the back of the lower GPU.
So, according to you, what's the best way to sync the Dynamo 360 with the HDPLEX 250 ?
Recreate a sync cable that plugs into a motherboard fan header or directly into the 4-Pin Sata connector of the HDPLEX ?
I understand you need a 5V and and GND wire.

All this allows me to downsize the current build to 11.9L, by :

- replacing the Corsair SF600 with the Meanwell combo,
- ditching the support for long GPUs.

A slim 140 fan placed on the front panel will bring fresh air to the four fans and blow on the Meanwell.
Everything is placed vertically, to help natural convection, and also because the case is placed under my small desk.

Any suggestion ?



Average Stuffer
Oct 16, 2017
I would say there are 3 options you can choose from.

Replace that PSU cluster with a single SFX/-L. There are still enough space for two Zotac Artic Storm 1080 ti Mini with length at 211mm

Still with the SFX, the intake side will be put against where the radiator fan is pulling air. The cards supported can be referenced size long, but height is limited to around 110mm

Third option is to have a PSU bracket for each GPU use case above. That is the compromise we have to make. It’s either length or girth, you cannot have both XD