Memory, Expansion Slots And Firmware
Mini-ITX motherboards are usually limited to two RAM slots because there just isn’t room for more. Intel’s H81 chipset is similarly limited to two slots, because only one DIMM per channel is supported; AMD’s AM1 has only a single channel, with up to two DIMMs, so those boards will also only have two RAM slots. You can easily add up to 16GB to a two-slot DDR3 board (32GB with DDR4), but if you need more, you’ll need to make sure that four DIMM slots are available (and usually start with a larger motherboard form factor).
Expansion Card Slots
Similarly, the size of the board you select will determine the number of expansion slots it might have, but the actual number and type will vary. Note also placement. If you need a PCIe x1 slot, make sure a single such available slot will not be blocked by a double-slot graphics card, which is common. Unlike PCIe x1 cards, M.2 SSDs typically will fit under the graphics cooler of an adjacent card. If you’re going to install a PCIe x4 RAID card, is that going to disable any other slots, or limit their bandwidth? Pore over specifications carefully if you have very precise requirements, and do not hesitate to post a request for suggestions in the Tom’s Hardware Forums!
If you have specific tasks to be performed by your PC, the components you install will make a bigger difference than the plethora of tweaking options. If, however, you enjoy working (or playing) with your PC as much as on it, or you anticipate needing to extend an aging computer’s useful life by speeding it up via overclocking, then you need to pay some attention to what the BIOS on the motherboard offers in the way of such tweaking, and you need to be sure that the voltage regulator modules (VRMs) are sufficiently robust to handle the additional power draw.
The more VRM phases the motherboard has, the lighter the load on each phase. If there is no heatsink on the voltage regulator, the motherboard is most likely not intended for overclocking, particularly of CPUs that already draw the maximum TDP the motherboard supports. This is particularly important on AMD motherboards, because most AMD CPUs (and APUs) are unlocked to allow overclocking; most Intel CPUs are not. Just because you can, doesn’t mean you should. Either way, make sure the motherboard you choose is up to the task.
Whether or not you can run RAID will be determined by the chipset you select, but set up in the firmware. Any RAID set you define may be managed by a software utility, but settings to enable it in the first place will be defined in the BIOS.
Buying a motherboard does not have to be difficult. As long as compatibility is assured across all part selections, with few exceptions even the cheapest low-end models ultimately meet most enthusiast needs.
A look at the successes of Dell, HP, and other pre-built system vendors is sufficient proof of that. However, many of these systems are designed with planned obsolescence in mind. Upgrades or expansion are unnecessarily difficult, because they are typically built with minimally specified parts. Upgrade one piece beyond that minimum and you may need to perform a cascade of other upgrades, and proprietary fit and connections will make that very costly or even impossible beyond a certain point.
As system builders, we want more and we want better. With a little foresight, if today’s system proves inadequate next year, a simple upgrade of the single insufficient component should do, and we can plan for that. Furthermore, even if we’ve chosen a budget board, we’re still likely to get all solid capacitors and more durable components than those used in the pre-built systems, so you can be sure your new motherboard will actually last through at least one upgrade cycle, likely more.
You’ll pay a premium for advanced features such as a robust BIOS that allows a range of performance tweaking, and for VRMs able to reliably sustain high overclocks. Being able to run two or more graphics cards adds to the price, especially for SLI.
The bottom line, though, is that with the exceptions of the outliers (AMD’s AM1 and Intel’s 2011[-v3]), many boards are suitable for many needs, accepting CPUs (or APUs) of varying speed and ability, allowing the use of plenty of storage, and with room to add more RAM or disk space as needed.
Finally, beginners have access to all the resources that professionals use to determine their needs, through review sites like ours and support communities like our Community Forums, where there are plenty of experienced builders all eager to help a newcomer join the ranks of enthusiasts who enjoy building and tweaking our own systems.