Mini ITX Builds
Why Mini ITX
Standard PC builds use ATX (Advanced Technology eXtended) motherboards housed in mid-tower or full-tower cases. These setups occupy significant desk or rack space — a typical ATX mid-tower is roughly 45—50 cm tall, 20 cm wide, and 45 cm deep. For homelabs, living-room PCs, or any space-constrained environment, this footprint is excessive.
Mini ITX is the smallest standardized motherboard form factor, measuring 170 mm x 170 mm. VIA Technologies introduced it in 2001 as a platform for low-power embedded systems, but over the years the ecosystem matured to support full desktop CPUs (Central Processing Units) and discrete GPUs (Graphics Processing Units). Today you can build a Mini ITX system that matches a full ATX workstation in compute power while fitting inside a case smaller than a shoebox.
The appeal is straightforward: desktop-class performance in a fraction of the volume. This makes Mini ITX the go-to form factor for SFF (Small Form Factor) builds — compact PCs that prioritize space efficiency without sacrificing capability.
Motherboard Form Factor Comparison
| Form Factor | Size (mm) | PCIe Slots | RAM Slots | Typical Use Case |
|---|---|---|---|---|
| ATX | 305 x 244 | 7 | 4 | Full desktop / workstation |
| Micro ATX | 244 x 244 | 4 | 2—4 | Budget / compact builds |
| Mini ITX | 170 x 170 | 1 | 2 | SFF builds |
| Mini DTX | 170 x 203 | 2 | 2 | Rare; slightly taller Mini ITX variant |
PCIe (Peripheral Component Interconnect Express) is the high-speed serial bus used to connect expansion cards — GPUs, network adapters, storage controllers — to the motherboard. The number of physical PCIe slots determines how many expansion cards you can install simultaneously.
RAM (Random Access Memory) slot count directly limits maximum memory capacity. With two slots, Mini ITX boards typically cap at 64 GB using 2 x 32 GB DIMMs (Dual Inline Memory Modules), though DDR5 (Double Data Rate 5) kits with 2 x 48 GB (96 GB total) are becoming available.
Key Constraints of Mini ITX
Mini ITX trades expandability for compactness. Before committing to this form factor, understand what you give up:
- Single PCIe slot. You get exactly one full-length PCIe x16 slot. If you install a discrete GPU, you cannot also install a PCIe network card, PCIe RAID controller, or any other PCIe add-in card. Any additional connectivity (10GbE networking, extra NVMe storage) must come from the motherboard’s built-in M.2 slots, USB ports, or Thunderbolt headers.
- Two RAM slots. Maximum memory is constrained by the largest available DIMMs. For DDR5, that currently means 64—96 GB. ATX boards with four slots can reach 128—192 GB.
- Limited onboard I/O. Mini ITX motherboards typically provide 1—2 M.2 slots for NVME SSDs (Solid State Drives) and 2—4 SATA (Serial ATA) ports, compared to 3+ M.2 and 6—8 SATA on ATX boards.
- Cooling challenges. Smaller cases restrict airflow. CPU cooler height, radiator mounting options, and fan placement are all constrained by case dimensions. Thermal throttling is a real risk if cooling is not planned carefully.
- Cable management difficulty. Less interior volume means cables compete for space with components. Modular PSUs (Power Supply Units) and custom-length cables help significantly.
Power Supplies for SFF Builds
Standard ATX PSUs measure approximately 150 mm x 86 mm x 140 mm — too large for most Mini ITX cases. SFF builds use smaller PSU form factors:
- SFX (Small Form Factor): 125 mm x 100 mm x 63.5 mm. This is the de facto standard for Mini ITX cases. Modern SFX units are available up to 850 W, sufficient to power a high-end CPU and GPU. Examples: Corsair SF750, Cooler Master V850 SFX.
- SFX-L: Same width and height as SFX but with a longer depth of 130 mm. The extra length accommodates a larger (120 mm) fan, which spins slower and produces less noise. Suitable for cases that explicitly support SFX-L — always check case specifications before purchasing.
- Flex ATX: 150 mm x 81.5 mm x 40.5 mm. The thinnest option, used in very compact or rack-mount-style cases. Flex ATX PSUs typically use a 40 mm fan spinning at high RPM, making them noticeably louder than SFX units. Available up to roughly 500—600 W.
TDP (Thermal Design Power) of the CPU and the power draw of the GPU determine the PSU wattage you need. A safe rule of thumb: add the CPU TDP, the GPU TDP, and 100—150 W for other components, then choose a PSU at or above that total.
Popular Case Categories
SFF cases fall into three main design families, each with different trade-offs:
Sandwich-Style
Examples: Dan A4-SFX, Cooler Master NR200, FormD T1.
The motherboard and GPU mount on opposite sides of a central spine or divider. This layout is extremely compact (often under 12 L in volume) but limits GPU length and thickness. Typical max GPU length is 295—310 mm with 2—2.5 slot thickness.
Traditional Tower
Examples: NCase M1, SSUPD Meshlicious, Lian Li A4-H2O.
A small tower layout with the GPU hanging below the motherboard (or mounted vertically via a riser cable). These cases support larger GPUs (up to 330—340 mm) and offer better airflow thanks to mesh panels and more fan mounting points. Volumes range from 14—20 L.
Console-Style
Examples: Fractal Design Ridge, Velka 3.
Low-profile horizontal layouts designed to sit under a TV or on a media shelf. They look like game consoles or AV equipment. GPU clearance is limited; many console-style cases only support low-profile or short GPUs.
Critical spec to check: GPU clearance. Every case specifies maximum GPU length, width (number of PCIe slots occupied), and sometimes thickness in millimeters. Measure your chosen GPU against these limits before purchasing the case.
Cooling in SFF
Thermal management is the hardest part of a Mini ITX build. The physics are simple: less volume means less air to move, and components are packed closer together.
CPU Cooling
- Low-profile air coolers (50—70 mm tall): Required by sandwich-style and console-style cases. Examples: Noctua NH-L9a (37 mm, handles up to ~65 W TDP), Noctua NH-L12S (70 mm, handles up to ~95 W TDP), ID-Cooling IS-60 EVO.
- Tower air coolers (120—155 mm tall): Fit in traditional tower SFF cases. Offer significantly better cooling than low-profile options. Examples: Noctua NH-U12A, Thermalright Peerless Assassin (if it fits).
- AIO liquid coolers: AIO (All-In-One) liquid coolers circulate coolant through a pump/block mounted on the CPU and dissipate heat through a radiator with fans. 120 mm and 240 mm radiator AIOs are common in SFF builds. A 240 mm AIO can comfortably cool CPUs with 105—170 W TDP. Examples: Arctic Liquid Freezer II 240, EK-AIO 240.
GPU Cooling
Most Mini ITX cases support GPUs occupying 2—2.5 PCIe expansion slots in thickness. Three-slot GPUs (common on high-end cards like the RTX 4080 or 4090) may not physically fit. When selecting a GPU for an SFF build, look for shorter, dual-slot or 2.5-slot models. Aftermarket “ITX-length” GPU variants (under 200 mm) exist for some models but are rare.
Mini ITX vs Mini PCs
Pre-built Mini PCs (e.g., Minisforum, Intel NUC, Beelink) are an alternative to building your own SFF system. The trade-offs differ significantly:
| Aspect | Mini ITX Build | Mini PC |
|---|---|---|
| Volume | 10—20 L | 0.5—2 L |
| Discrete GPU | Yes (full PCIe x16 slot) | No (integrated graphics only, or eGPU via Thunderbolt) |
| CPU options | Desktop CPUs (higher clocks, more cores) | Mobile/laptop CPUs (lower TDP, lower peak performance) |
| Upgradability | Full (swap any component) | Limited (RAM and storage only, sometimes soldered) |
| Power consumption | 200—500 W under load | 15—65 W under load |
| Noise | Depends on cooling setup | Generally quiet |
| Assembly | You build it yourself | Ready to use |
For workloads that require a dedicated GPU — such as running LLM (Large Language Model) inference with Ollama, training ML (Machine Learning) models, or GPU-accelerated video transcoding — a Mini ITX build is typically the smallest option that avoids the bandwidth penalties of an eGPU enclosure. Thunderbolt 4 provides approximately 32 Gbps to an eGPU, while a direct PCIe 4.0 x16 slot provides 256 Gbps — an 8x difference that matters for GPU-intensive tasks.
Example Mini ITX Homelab Build
A concrete build targeting local LLM inference and homelab virtualization with Proxmox VE:
| Component | Selection | Notes |
|---|---|---|
| Case | SSUPD Meshlicious | 14.6 L volume, mesh panels for airflow, supports 240mm AIO and full-length GPUs up to 336 mm |
| CPU | AMD Ryzen 7 7800X3D | 105 W TDP, 8 cores / 16 threads, AM5 socket |
| Motherboard | ASUS ROG Strix B650-I | Mini ITX, AM5 socket, 1x PCIe 4.0 x16, 2x M.2 slots, WiFi 6E, 2.5GbE LAN |
| RAM | 64 GB DDR5-5600 (2 x 32 GB) | Fills both DIMM slots to max practical capacity |
| GPU | NVIDIA RTX 3060 12 GB | 12 GB VRAM sufficient for running 7B—13B parameter LLMs via Ollama; 242 mm length fits easily |
| Storage | 2 TB NVME SSD (PCIe 4.0) | Primary OS + VM storage on the first M.2 slot |
| PSU | Corsair SF750 | SFX, 750 W, 80+ Platinum efficiency; comfortably powers this build (total draw ~300 W under load) |
| Cooler | 240 mm AIO (e.g., Arctic Liquid Freezer II 240) | Mounted on the side bracket of the Meshlicious; keeps the 7800X3D well under thermal limits |
Total estimated volume: 14.6 L. Total estimated power draw under full CPU + GPU load: approximately 280—320 W.
See also
- NVME — the storage interface used by modern SSDs in M.2 slots
- External GPUs (eGPUs) — an alternative to a discrete GPU in a Mini ITX build, using Thunderbolt enclosures
- Proxmox VE — a virtualization platform well-suited for homelab builds