A guide to SFF PCs (Draft)

A Guide to SFF PCs

Welcome to the guide to SFF PCs.

Introduction to SFF PCs

In this section, we will explore different aspects of SFF PCs, including their components and software, with a focus on Linux and open-source solutions.

What is an SFF PC?

An SFF PC is a Small Form Factor PC. It is usually very compact, power-efficient, and can be used for various purposes. They are commonly found in schools, offices, and home servers.

Why should I choose an SFF PC?

There are many reasons to choose an SFF PC:

• Compact: SFF PCs are very small and can fit almost anywhere. (~1-3 liters)
• Power-efficient: They consume less power, especially models with T or U series processors.
• Affordable: SFF PCs are often cheaper than traditional desktop PCs, especially on the second-hand market.

Why shouldn't I choose an SFF PC?

There are also some drawbacks to consider:

• Limited upgradeability: Many SFF PCs have limited upgrade options, and some components are not replaceable.
• Fewer ports: Compared to larger desktops, SFF PCs typically have fewer connectivity options.
• Performance constraints: Due to their small size and thermal limitations, performance may be lower than full-sized PCs.
• Proprietary components: Some models use proprietary parts, making repairs and upgrades more difficult.

What are some examples of SFF PCs?

Here are some well-known brands and models:

• Lenovo ThinkCentre: M73 Tiny, M710q, M720q, M70q G1, M75q G1, M90q G3
• Dell OptiPlex: 3040, 3050, 3060, 3070, 5040, 5050, 5060, 5070
• HP EliteDesk: 800 G1 Mini, 800 G2 Mini
• Intel NUC: NUC6i3SYH, NUC6i5SYH, NUC6i7KYK, NUC7i3BNH, NUC7i5BNH, NUC7i7BNH
• Zotac ZBOX: CI660 Nano, CI640 Nano, CI620 Nano, CI540 Nano, CI520 Nano, CI327 Nano
• Asus VivoMini: UN65, UN65U, UN65U-M023M, UN65U-M021M, UN65U-M022M, UN65U-M020M

Many other brands and models are available on the market.

For second-hand options, i recommend Lenovo, Dell, and HP. These brands offer plenty of affordable models that are often upgradable (RAM, SSD, CPU, PSU).

ARM SFF PCs

SFF PCs are usually x86-based, but ARM-based SFF PCs have been gaining popularity in recent years. They are generally cheaper and more power-efficient but come with limitations:

• Limited software compatibility: They are not compatible with traditional x86/PC software.
• Limited upgrade options: Components are often soldered and non-replaceable.
• Lower performance: Compared to x86 counterparts, ARM-based SFF PCs may struggle with demanding tasks.

In this guide, we will focus on x86 SFF PCs and the Raspberry Pi.

SFF PC Components

In this section, we will look at the main components of SFF PCs.

CPU (Central Processing Unit)

I recommend using socketed CPUs, as they allow for future upgrades to more powerful models (within the same TDP range). For example, you can upgrade from an Intel Celeron G4900T to an Intel i9-9900T without any issues or with a BIOS update.

Most SFF PCs come with 35W or 65W CPUs, i strongly recommend avoiding CPUs with a higher TDP than what the system supports, as this can cause overheating and potentially damage the motherboard or PSU.

Most modern software utilizes AVX and AVX2 instructions, which can significantly boost performance in tasks like video encoding/decoding, compression, encryption, etc. Every CPU since Intel Haswell and AMD Zen supports AVX2, except for some low-end models like Intel Celeron/Pentium and AMD Athlon.

SFF PC Components

In this section, we will look at the key components of SFF PCs.

CPU (Central Processing Unit)

I recommend using Intel Coffee Lake, AMD Zen 2, or newer CPUs, they offer nice performances and support modern features like NVMe, iGPU Vulkan, HEVC/VP9 10-bit hardware encoding/decoding, AVX2, etc... However, if you’re on a budget, Haswell or Skylake remains a good option due to the low price of the CPUs and relatively good performance.

GPU (Graphics Processing Unit)

Most SFF PCs have only an integrated GPU, they are sufficient for light GPU tasks and are very power efficient, some SFF PCs can add a dedicated GPU (like M720Q/M920Q), these are low-profile and use PCIe x4/x8 lanes, which can be useful for light gaming, networking, etc... Ensure the PSU and motherboard can support the PCIe card's power consumption.

RAM (Random Access Memory)

SFF PCs typically have two RAM slots, supporting DDR3, DDR4, or DDR5 RAM depending on the CPU and motherboard, the maximum capacity usually ranges from 16GB to 128GB, i recommend using two identical RAM sticks to enable dual-channel (double the bandwidth), you can use higher-frequency RAM than what the CPU officially supports; the RAM will simply downclock to the CPU-supported frequency.

Most SSF PCs support SO-DIMM (RAM in Laptop), which is smaller than standard DIMM RAM, but they have similar performances.

I recommend using DDR4 or DDR5 RAM, as it is the most common, well-supported, and cost-effective option. Here are some general recommendations (in 2025):

• 4GB: Barebones Linux server, light applications. (small website hosting, router, NAS)
• 8GB: Light to medium applications. (web browsing, office work, small servers)
• 16GB: Recommended for most use cases. (gaming, basic game server, CI build server, light development)
• 32GB+: Optimal for multitasking. (AAA gaming, video/photo editing, rendering)
• 64GB+: Heavy multitasking. (virtualization, machine learning, scientific computing, CAD)

Storage

SFF PCs have four main storage options (depending on the model):

• M.2 NVMe SSD: Very fast and present in most SFF PCs since 2015, the best choice.
• M.2 SATA SSD: Uses the same connector as NVMe but operates at SATA speeds. (e.g., ThinkCentre M700)
• 2.5" SATA SSD: Slower than M.2 NVMe but a good alternative if M.2 is unavailable.
• 2.5" SATA HDD: Very slow and generally not recommended, but can be replaced with an SSD.
• Onboard eMMC: Soldered storage on the motherboard, avoid it, it is slow, limited and non-replaceable.

I recommend using M.2 NVMe SSDs, be mindful of the size (2242, 2260, 2280), connector type (B, M, B+M), and whether it's single- or double-sided.

Ports

All SFF PCs have a limited number of ports, ensure that your chosen SFF PC has enough ports for your needs, some models support expansion for additional ports (M710Q, M720Q).

Common ports include:

• USB 2.0/3.x: For peripherals, storage
• HDMI/DisplayPort/VGA: For monitors
• Ethernet: For networking
• Audio jacks: For headphones, microphones, speakers

PSU (Power Supply Unit)

Most SFF PCs use an external power supply, often with a proprietary connector.

Here are general guidelines:

• 65W: 35W CPU
• 90W: 65W CPU or 35W CPU + DVD drive/expansion
• 135W: 65W CPU + 45W GPU or 100W CPU

Using an under-dimensioned power supply can damage it.

Motherboard

Like the PSU, most SFF PCs have a proprietary motherboard. Sometimes, you can replace it with another model from the same brand (e.g., an M920Q motherboard in an M720Q). However, in most cases, it is best to stick with the original motherboard model.

Lenovo thinkcentre SSF PCs

In this section, we will see the different models of Lenovo thinkcentre SSF PCs.

¹: You need proprietary riser card to use the PCIe slot

M720q and M920q

CPU

The M720q supports all 8th and 9th generation Intel 35W CPUs (models with T suffix), the i7-9900T is the most powerful CPU available for this model, but it is very expensive and hard to find, the i3-8100T, i3-9100T, i5-8500T, i5-9500T, i7-8700T, i7-9700T are far more common, often affordable and offer good performances.

Avoid celeron and pentium CPUs, they are very slow (missing AVX2, FMA3, etc...), do not use CPUs with a higher TDP than 35W, this can cause overheating and potentially damage your motherboard or PSU.

RAM

The M720q have two DDR4 SODIMM slots with a maximum capacity of 64GB (2x32GB), the maximum frequency is 2400MHz or 2666MHz on i5/i7 CPUs, you can use higher frequency RAM, it will downclock to the CPU supported frequency.

I recommend using two identical RAM sticks to enable dual-channel (double the bandwidth), at least 8GB, 16GB is optimal for multitasking, 32GB is recommended for heavy multitasking.

Storage

GPU

All compatible CPU have an integrated GPU, they are sufficient for most light GPU tasks (web browsing, play video, etc...), if the iGPU is not enough, you can add a low-profile GPU with proprietary PCIe riser card, you are limited with PCIe 3.0 x8 and 45W TDP. (you also need 135W PSU)

PSU

The proprietary PSU used for the M720q has a 65W, 90W, 135W power rating, 90W is minimum when you use expansion cards or powerful CPU. (i7 or i9 CPU)

Expansion and accessories

The M720q supports multiple expansion options:

Sources

• Project TinyMiniMicro
• Tiny/Mini/Micro PC experiences
• Wikipedia
• cpu-world