Nowadays, it is easy to find a new hobby. But it is much harder to find a hobby, which could last forever and bring new challenges all the time. For me, such kind of hobby becomes building mini-ITX PCs. It has two main reasons: multiple restrictions and new hardware releases.
I’ll skip the second point because it is obvious for all that tech companies and even small custom manufacturers tend to release something new a couple of times per year.
But the main cause I love this hobby is the multiple restrictions during the build. The biggest restriction is the size of the case. Size definitely matters here. According to the web, the max size considered as SFF is 20L, which is a bit less than half of the PS5 volume. SFF PC builders likes to target smaller than the max size. The minimum size I have built was 3.3 liters, which is three times smaller, than PS5.
The next important thing is hardware layout. Apart from the default vertical layout for tower cases, exists a sandwich layout. It allows to minimize case size but has its cooling restrictions due to the small distance between CPU and GPU. Also, it requires a razer to connect GPU to your MOBO and it could cost a lot.
For the cube SFF cases vertical layout changes to horizontal. Last but not least is the cases without a place for GPU. Such kinds of cases allow extreme volume optimization but couldn’t be enough powerful for AAA gaming.
The motherboard is probably the only easy choice because most of the SFF cases could accommodate only mini-ITX boards. The only exception is mini-DTX boards, which slightly larger but rare and expensive, so just a handful of cases support it.
Mini-ITX MOBOs have only 2 slots for RAM, so it is always required to buy the best kit you could. But even here you should think about the height of the RAM. Fancy RGB kits or kits with a huge heatsink could be too high for your CPU cooler or case. Low-profile RAM is a good choice but it isn’t always best looking.
For the CPU the only restriction is the power of your cooling system. It is even possible to use server CPUs AMD Threadripper and Intel Xeon. For the smallest cases, it is possible to use only low profile coolers that could handle relatively cold chips or try to undervolt the CPU.
Bigger SFF cases could fit into powerful tower CPU coolers and AIOs. Some of the cases allow building custom water loops but it is out of my league right now.
GPU size and its power consumption are two main issues. The most powerful cards from AMD and Nvidia most likely will not fit into extreme cases with a volume of fewer than 6–7 liters. At this moment it wasn’t released any mini-ITX versions, hope it will change soon. A bit bigger could accommodate two slot cards but you should pay attention to its and case’s dimensions. It would be a disaster if GPU wouldn’t fit by a couple of millimeters.
In order to power the system, we have to choose the appropriate PSU. There is a big range of PSU types: pico PSU for the smallest cases, flex ATX for slightly bigger versions, and also SFX and SFXL for non extremely small cases and powerful systems. Apart from the power of the PSU, we should always think about cables. Sometimes only shorter custom cables could flawlessly fit into your build.
When the build is finished, tests are coming. Noise and heat parameters are crucial at this moment because the case has to be near the monitor. Sometimes you have to add one more fan or remove one. Tweak fans curve. Sometimes you have to change the PSU fan to a custom and also replace cables. Try to underclock the CPU and GPU. Or change the cooling system from a fan to an AIO. Only then you could be satisfied with the build because it is in a beautiful small body, more powerful and efficient than any console by a mile!
Then try once again. There is always exists room for improvement or new case or new hardware ).