Resource Cheatsheet
A+ Core 1 3.5: Motherboard Form Factors
A+ Core 1 3.5 — ATX vs micro-ATX vs Mini-ITX: size, slots, power (20/24-pin) and shared ATX mounting.
- Updated
- Reading time
- 3 min read
- Detail
- A+ Core 1
- Detail
- Motherboard Form Factors
On this page
In one line: three boards to know — ATX (largest, most slots), micro-ATX (smaller, ATX-compatible), Mini-ITX (smallest) — all sharing ATX mounting points.
Companion to: Professor Messer A+ Core 1 (220-1201), Section 3, objective 3.5. The full version is the Motherboard Form Factors class notes; the section overview is the Section 3 sheet.
The three form factors
| ATX | micro-ATX | Mini-ITX | |
|---|---|---|---|
| Size | Largest | Middle | Smallest |
| Full name | Advanced Technology Extended | Micro-ATX | Mini-ITX |
| Appeared | 1995 | From ATX | From ITX |
| Expansion slots | Most | Fewer | Fewest (often one) |
| Memory slots | Most (e.g. 4) | Fewer (e.g. 2) | Fewest |
| Main power | 20-pin → 24-pin | Same as ATX | Same family |
| Mounting points | ATX standard | Same as ATX | ATX-compatible |
| Fits ATX case | Yes | Yes | Yes |
| Dimensions* | ~305 × 244 mm | ~244 × 244 mm | ~170 × 170 mm |
*Dimensions are for reference — the exam leans on the relative ordering, not the millimetres.
Choosing by scenario (objective 3.5 is scenario-based)
| Job | Pick | Why |
|---|---|---|
| 4K video-editing desktop | ATX | Most slots, most RAM, best cooling room |
| Small office, room to grow | micro-ATX | ATX-compatible, smaller, a slot or two spare |
| Media box beside the TV | Mini-ITX | Smallest, quiet, single task |
- Rule: pick the smallest board that still gives the expansion and cooling the job needs.
- More slots is a tendency of size, not a guaranteed spec — the maker decides how many to fit.
🔐 Security notes
- A standard footprint helps an attacker too: a tampered same-form-factor board drops into the same chassis and looks right (supply-chain / evil-maid). Physical asset checks — expected board, slot count, populated headers — catch it.
- Small single-purpose boxes are still endpoints: Mini-ITX appliances by a TV, at reception or in a cupboard are exposed and often unpatched. Inventory, patch and segment them; don’t leave “just the media box” unmanaged on the LAN.
Practice drills
1. Name the three form factors in size order.
ATX (largest) > micro-ATX (middle) > Mini-ITX (smallest).
2. What does ATX stand for, and when did it appear?
Advanced Technology Extended, 1995.
3. How did the ATX main power connector change?
From a 20-pin connector on early boards to a 24-pin on modern ones.
4. Two things micro-ATX keeps the same as ATX?
The mounting points and the power connectors.
5. Why does a Mini-ITX board fit an ATX case?
It keeps ATX-compatible mounting screw points, so the holes line up with the case standoffs.
6. A customer wants a quiet streaming box for the living room. Which board?
Mini-ITX — smallest footprint, fits a tight space, needs almost no expansion.
7. True or false: a bigger board guarantees more expansion slots.
False — a bigger board makes more slots possible, but the manufacturer decides how many to fit.
Key takeaways
- Three to know: ATX (largest, most slots) → micro-ATX (smaller, ATX-compatible) → Mini-ITX (smallest).
- ATX = Advanced Technology Extended, 1995; main power 20-pin → 24-pin.
- micro-ATX shares ATX’s mounting points and power; fewer slots.
- Mini-ITX keeps ATX-compatible mounting, so it fits an ATX case; ideal for single-task builds.
- Objective 3.5 is scenario-based: choose the smallest board that meets the job’s expansion and cooling needs.