Building a Small Form Factor PC

I’ve wanted to build a small form factor PC (SFFPC) for quite some time. One of my favourite technology YouTube channels is Optimum Tech, and the host specializes in building small ITX form factor PC builds. At this point, building a SFFPC is not super niche, and there’s a sizeable community surrounding it.

The Case

SFFPC builds revolve around the PC case, because that’s what limits the size, and to some extent, the power¹ of the build. SFFPC expert, Optimum Tech, has a really high opinion of the FormD T1.

The FormD T1 comes in three possible layouts: the reference layout, the tower layout, and the sandwich layout. Optimum Tech argues that the sandwich layout provides the best cooling performance, and so I purchased a FormD T1-SW case in all black. It arrived flat-packed after a few weeks, and I used the online manual to assemble it together. Assembly was surprisingly straightforward and clear, thanks to the manual.

I did not yet install the panels, because I still have a computer I need to put in it!

Testing the Power Supply

I’m using a Corsair SF750 power supply, which is probably the most popular ITX form factor PSU. Before assembling all my parts together, I tested the integrity of the PSU with a PSU tester, for my peace of mind. I connected the various pins from the PSU to the PSU tester, and checked that the voltage readings were all correct.

Assembling the Motherboard

I’m using an AMD Ryzen 9 3900X as my CPU with a Gigabyte B550I Aorus Pro AX motherboard.

I have some fan cables plugged in.

For the CPU cooler, I’m opting for a Noctua NH-L12 (Ghost S1 Edition) air cooler. Installing the cooler on my AMD motherboard requires that I screw in AM4 brackets and spacers.

I uninstall the hex standoffs that I had installed around the CPU, previously. Instead, I install the long AM4 brackets, so that the CPU cooler is oriented in such a way that it doesn't collide with the RAM and the motherboard's VRAM.

I apply some CPU cooler—not too much though, because everyone on the internet likes to go on and on about how if you apply too much cooling paste, the cooling efficiency decreases. I then screw the CPU cooler in place above the CPU using a long screwdriver.

The CPU cooler just barely makes clearance against some of the capacitors on the motherboard.

We then place the motherboard into the case.

The FormD T1 includes some hex standoffs that raise the motherboard a little above the case skeleton. If you look carefully, you can see that the surface of the CPU cooler isn't actually parallel with the case---probably because the CPU cooler is pretty heavy. It doesn't bother me though.

Installing the Power Supply

Next, we install the power supply unit. The FormD T1 comes with a bracket for mounting the PSU. I use some screws to mount the PSU onto the bracket.

In the second photo, you can see the PCIe riser cable. I talk about installing the cable immediately below.

Installing the GPU

I then install the GPU. I’m using a MSI RTX 3070 Ventus 2X.

30-series GPUs require a PCIe 4.0 connection, so I use a Louqe Cobalt PCIe 4.0 riser cable to connect the GPU to the motherboard. I also use a threaded block that comes with the FormD case to secure the GPU to the PC case.

The first photo shows the end of the PCIe cable that connects to the GPU. The second photo shows the block that secures the GPU to the PC case. The final photo shows off the installed GPU.

I then plugged in custom-length cables from Pslate Customs into the PSU.

The custom-length cables going from the PSU to the motherboard.

The GPU requires an adaptor that converts a 2x4 pin set into two 2x4 pin sets.

The GPU adaptor cable.

Installing Exhaust Fans

Proper cooling is critical for SFFPC builds. I installed two Noctua NF-A12x25 fans to the top of the case, so that they exhaust hot air from the inside of the PC to the outside. Installing the fans is straightforward. The Noctua fans come with self-tapping screws, and they secure the fans against some slots in the case. The two fans’ cables are connected via a splitter, and the end of the splitter is plugged into SYS_FAN1 on the motherboard. I also used some zip ties to clean up the cabling.

Installing the Power Switch

The FormD T1 uses a very discrete button located on the side of the front panel to power on the machine. I find this button really unsatisfying to use, however, and even worse, I’m not always sure whether or not I’ve pressed it, because the button has very little tactility and travel distance. So I instead use this very discrete button as a resest switch, by plugging the leads into the reset pins on the motherboard. The motherboard’s user manual identifies these pins.

The polarity of the power switch and the reset switch do not matter. These switches just close or open the circuit.

For the power button, I wanted to make use of the big M19 threaded holes at the back of the case. FormD actually sells M19 power switches on their online shop, but it’s frequently out of stock. Fortunately, I found a M19 push button switch on Amazon that works perfectly. The switch is supposed to light up as well, but I couldn’t seem to get the LED working with the LED pins on the motherboard.

I soldered and heat shrunk the leads on the push button, and then screwed the button into one of the M19 threaded holes on the rear of the PC case.

Finishing Touches

Even though I couldn’t get the LED that’s built into the push button switch to work, I still wanted a power status LED. Fortunately, I have a bunch of LEDs lying around. I wired up a white LED to the motherboard’s Power LED pins, and I Kapton taped it to the inside of the PC case’s front panel.

It’s a beautiful work of art.

Finally, I wanted to do something about the other M19 threaded hole that’s gaping open at the back of the case. The case has two M19 holes, and I used the power switch to cover one of the holes. Fortunately, FormD suplies .stl files for 3D-printing threaded caps that can cover the M19 holes. I found the dimensions of the threaded cap to be a little too snug, however, so I adjusted the file’s x and y scaling in Prusa Slicer to 98%. With this slight adjustment, the print came out perfectly.

Fan Configuration

The PC is totally usable now! We can use it for all sorts of things, including more intense workloads like video games, CAD, and video editing work. Before we call it a day though, we’re going to want to configure the fans. SFFPCs are small, and so they can build up a lot of heat inside the computer. We want to try and optimize the computer’s cooling performance.

By default, fans that are plugged into the motherboard will ramp up based on CPU temperature. So, the Noctua exhaust fans we installed will ramp up as the CPU temperatures get higher. We don’t want this relationship, however. Instead, we want our exhaust fans to ramp up as the GPU temperatures get higher. To estbalish this relationship, we have to use a program called Argus Monitor. Optimum Tech shows how to use this program in this video at 20:59.

My Argus Monitor settings. Recall that both my exhaust fans are plugged into SYS_FAN1 via a fan splitter. So we have one fan port controlling two fans.

GPU Undervolting

Everyone in the SFFPC world recommends undervolting the GPU. Undervolting the GPU results in quieter and cooler operation, with no cost to performance. Again, Optimum Tech explains how to undervolt the GPU in this video at 21:36. We use a software called MSI Afterburner to undervolt the GPU.

My GPU undervolt curve in MSI Afterburner.

Future Improvements

All in all, I’m very happy with the build! I think the only thing I might want to add in the future is a front IO panel.

You can see the white power LED glowing in the second picture.

Parts Summary

Item	Part
Case	FormD T1 Sandwich Kit
PSU	Corsair SF750 power supply
CPU	AMD Ryzen 9 3900X
CPU Cooler	Noctua NH-L12 (Ghost S1 Edition)
Motherboard	Gigabyte B550I Aorus Pro AX
RAM	Corsair Vengeance LPX 64GB (2 x 32GB) DDR4 DRAM 3200MHz
SSD	Samsung 970 Evo Plus 1 TB
GPU	MSI RTX 3070 Ventus 2X
PCIe riser	Louqe PCIe 4.0 riser cable
Exhaust Fans	Two Noctua NH A12x25 fans
Power Switch	Ulincos Momentary Pushbutton Switch U19D1 1NO SPST for 19 mm mounting hole

Footnotes

1. You can still build very poweful computers in ITX cases, without creating the world’s desnsest space heater. In many ways, the engineering challenge of trying to build the most powerful computer in the smallest space is what draws people into the SFFPC world. People have come up with clever ways of efficiently disippating heat from even the most power hungry hardware. ↩