Stew Machine - a Steam Machine Replica

Stew Machine - a Steam Machine Replica

The newly released Steam Machine is, without a doubt, an interesting piece of hardware. Its form factor, minimalist design, user experience, and HDMI-CEC support make it a perfect companion for a living-room TV.

Personally, since I already have a high-end PC, I'm not particularly interested in its performance. Instead, I would use it as a dedicated machine for emulation, 2D platformers, and LAN game streaming—without having to rely on the rather inadequate built-in Android system on my TV.

Given its relatively high price, limited availability, and iconic design, I thought it would be worth turning my bin of old hardware, left over from previous upgrades, into a (nearly) exact replica of the Steam Machine—or at least its chassis.

How exact? It has exactly the same dimensions and is even compatible with the original faceplate.

The most interesting part, in my opinion, is that the hardware can be replaced and upgraded. This allows for low-budget builds (like mine), while also making it possible to build systems that can outperform the original Valve hardware.

What is it?

Basically, this is an SFF case compatible with ASRock DeskMini motherboards, featuring an internal M.2 NVMe-to-PCIe eGPU dock and a 300 W power supply.

Does it make sense?

This is a fairly advanced build, and I don't provide step-by-step instructions.

Some GPU performance may be lost due to the PCIe x4 connection. In my opinion, this project only really makes sense if, like me, you already have most of the hardware lying around, are curious about the Steam Machine, and are looking for a fun project to build.

Temperatures

Surprisingly, even with the faceplate installed, the CPU stays below 70 °C, thanks to the rather overkill CPU cooler.

On the other hand, while my W6400 keeps its temperature below 80 °C, its fan becomes audible with the faceplate installed and no case fans.

Hardware compatibility

• Motherboard: ASRock DeskMini. The shared model was designed around the DeskMini 310 motherboard. Other DeskMini models will probably fit as well, but I haven't been able to confirm this.

• CPU: Check compatibility with your specific motherboard. CPUs with a TDP of ≤65 W should be supported. More powerful CPUs, when compatible, should be power-limited through the BIOS to avoid overloading the weak VRMs.

• CPU cooler: 90 mm-wide tower cooler, with a maximum height of 134 mm. For my build, I went with a completely overkill Chinese dual-tower single fan cooler with six heatpipes by Adegrees.

• GPU: Single-slot or dual-slot low-profile GPU, with a maximum length of 168 mm and no dedicated power connectors. Examples:

  • AMD Radeon Pro W6400 / RX 6400

  • NVIDIA RTX A2000

  • Intel Arc B50 Pro

• Storage: The only NVMe slot on my motherboard is occupied by the GPU, so I had to use a 2.5" SATA SSD instead. Other DeskMini motherboards support two NVMe slots.

• Case fans: With a single-slot GPU, it is possible to install an additional 40x20 mm fan at the front and a 92 mm slim fan at the rear.

Technical details

RGB LED

The integrated LED strip is fully addressable and can be configured using software such as OpenRGB.

The problem is that my DeskMini motherboard doesn't have any ARGB/RGB headers. As a workaround, I connected a SparkFun Pro Micro to the USB 2.0 header and flashed it with the CorsairLightingProtocol firmware. I use it to emulate a Corsair Lighting Node PRO, just smaller and cheaper.

In iCUE, I set the controller's default color to blue, so the LEDs stay blue whenever they aren't being controlled by software.

PSU

The power supply is a Mean Well LOP-300-12, which can provide between 180 W and 300 W depending on ventilation conditions.

Although the DeskMini is officially specified as compatible only with 19 V power supplies, it seems to work perfectly fine with 12 V in my setup. The advantage is that I can power both the motherboard (through a hidden internal connection) and the eGPU dock from a single power source.

DIY eGPU dock

The eGPU dock is based on an M.2 NVMe-to-PCIe x4 riser.

To make sure the GPU is powered only when the PC is switched on, I added a small MOSFET power-switch module to the build. It consists of P-channel MOSFETs that provide 12 V only when they detect a trigger voltage from a fan header, USB, SATA, etc. In my case, I used a fan header as the trigger.

I also removed almost all of the module's connectors and soldered the wires directly to the board to simplify the wiring and save space.

Power button

Due to space and aesthetic constraints, the power button in my design presses sideways against the plunger of a tactile switch. While this solution works reliably once installed, it does require a bit of fiddling during assembly. I had to trim small pieces off the button until I found the right shape and got a satisfying click.

BOM (non-PC hardware)

• Mean Well LOP-300-12

• M.2 NVMe-to-PCIe x4 riser https://www.amazon.it/dp/B0FJRHVLPL

• MOSFET module: https://it.aliexpress.com/item/1005011600608523.html

• ~20× M3×8 hex socket screws

• 4× M3×6 countersunk screws (for the SATA drive and C14 socket)

• M3 L4 mm OD 4.5 mm threaded brass inserts

• IEC C14 panel-mount socket https://amazon.it/dp/B00HUHAB0U

• JST VH 3.96 mm 3-pin connectors (for the PSU): https://www.amazon.it/dp/B0DNPJ3GXT

• JST XH 2.54 mm 4-pin connectors (for USB and FAN headers)

• JST PH 2.0 mm 4-pin connectors (for the power switch and status LED)

• 6×6 mm tactile PCB switch with long stem (for the power button)

• 3mm led diode (status led)

• SATA extension cable (data + power)

• WS2812B COB LED strip, 160 LEDs/m, 5 mm https://it.aliexpress.com/item/1005007760279947.html

• SparkFun Pro Micro

• 5.5×2.5 mm 90° DC male barrel plug (used without its outer casing to power the motherboard): https://it.aliexpress.com/item/1005005429978517.html

• Fan hub: https://www.amazon.it/dp/B082W5YV91

• wifi/bluetooth antennas https://www.amazon.it/dp/B0FKKZ9MKR

• 4x 6x3mm magnets (faceplate)

• misc consumables (glue, double sided tape, wires, solder...)

3D printing

The case can be printed on virtually any 3D printer and does not require supports, except for back_cover.

All external faces of the case should be printed flat, facing the build plate.

io_plate should be glued to back_cover by melting the plastic with a soldering iron.

Parts with the _modifier suffix should be set as Modifier parts in PrusaSlicer with the following settings:

• 0 top/bottom layers

• Honeycomb infill pattern

Example use of modifier parts:

front_vent, back_cover and  left_sidepanel are available in different variants depending on the GPU configuration.

Disclaimer

I don't provide step-by-step assembly instructions, partly because this build involves working with mains AC voltage, which can be dangerous if handled improperly.

The CAD files are provided so that anyone interested can inspect, modify, and remix the design freely. Feel free to adapt the case to your own hardware and requirements.