Quick Answer: ATX motherboards measure 12 × 9.6 inches and work with standard PC cases, while EATX (Extended ATX) boards are larger at 12 × 13+ inches, offering more expansion slots and features but requiring compatible cases. Choose ATX for gaming and general use, EATX for workstations and high-performance builds.
When building or upgrading a PC, your motherboard choice affects everything from case compatibility to future expansion potential. The form factor—essentially the size and layout standard—determines what components you can install and which cases will fit your build.
Let’s break down the key differences between these two popular motherboard formats so you can make the right choice for your specific needs.
🔧 What is ATX? The Standard That Changed PC Building
ATX (Advanced Technology eXtended) emerged in 1995 when Intel recognized the need for better PC standardization. Before ATX, computer cases had poor airflow, difficult upgrade paths, and inconsistent layouts.
ATX Specifications:
- Dimensions: 12 × 9.6 inches (305 × 244 mm)
- Mounting Points: 9 standardized screw holes
- I/O Panel: Rear-mounted ports for easy access
- Power Connector: 24-pin main power + 4/8-pin CPU power
Typical ATX Features:
- 4 DIMM slots (up to 128GB RAM)
- 1 PCIe x16 slot, 2-3 PCIe x1 slots
- 6-8 SATA connectors
- Integrated audio and network controllers
📏 Understanding EATX: When Standard ATX Isn’t Enough
Extended ATX takes the ATX foundation and expands it for users who need more—more RAM slots, more expansion cards, or dual CPU support. However, unlike ATX’s strict standardization, EATX dimensions can vary between manufacturers.
EATX Specifications:
- Standard Dimensions: 12 × 13 inches (305 × 330 mm)
- Variable Width: Can extend beyond 13 inches depending on manufacturer
- Enhanced Mounting: Additional support points for larger board
- Power Requirements: Often needs dual 8-pin CPU power connectors
EATX Advantages:
- 8+ DIMM slots (up to 512GB+ RAM)
- Multiple PCIe x16 slots for multi-GPU setups
- Dual CPU socket support on some models
- Enhanced power delivery systems
- More onboard controllers and features
⚖️ ATX vs EATX: Side-by-Side Comparison
| Feature | ATX | EATX |
|---|---|---|
| Size | 12″ × 9.6″ (305 × 244mm) | 12″ × 13″+ (305 × 330mm+) |
| RAM Slots | 4 DIMM slots | 8+ DIMM slots |
| PCIe Slots | 1 x16, 2-3 x1 | 2-4 x16, 4+ x1 |
| Price Range | $80 – $400 | $200 – $800+ |
| Best For | Gaming, general use | Workstations, servers |
🏠 Case Compatibility: The Make-or-Break Factor
This is where many builders run into trouble. Your motherboard choice directly impacts which cases you can use.
ATX Case Requirements
ATX motherboards fit in:
- Mid-tower cases: Most popular option, good balance of size and features
- Full-tower cases: Plenty of room, excellent cooling potential
- Some compact cases: Check clearance for components
EATX Case Considerations
EATX boards need:
- Full-tower cases: Essential for proper fit
- EATX-specific cases: Look for explicit EATX support
- Server/workstation chassis: Often the only option for extreme EATX boards
🎯 Which Form Factor Should You Choose?
Choose ATX When:
- ✅ Building a gaming PC with single GPU
- ✅ Budget is under $2,000
- ✅ Using standard desktop components
- ✅ Want maximum case compatibility
- ✅ Don’t need more than 64GB RAM
Choose EATX When:
- ✅ Running multiple GPUs for rendering/AI
- ✅ Need 128GB+ RAM for professional work
- ✅ Building a server or workstation
- ✅ Want maximum future expandability
- ✅ Budget allows for premium components
🔧 Installation and Setup Differences
ATX Installation
1. Install I/O shield in case 2. Mount motherboard standoffs (9 points) 3. Place motherboard and secure with screws 4. Connect 24-pin power + 8-pin CPU power 5. Connect front panel connectors
EATX Installation
1. Verify case clearance for full board width 2. Install I/O shield and additional standoffs 3. Mount motherboard (may require 2 people) 4. Connect dual 8-pin CPU power + 24-pin 5. Plan cable routing carefully due to size 6. Ensure adequate PSU capacity (750W+)
📊 Quick Decision Matrix
| Your Need | Recommended Choice | Why |
|---|---|---|
| Gaming PC | ATX | Cost-effective, plenty of features |
| Content Creation | EATX | More RAM slots, multiple GPUs |
| Budget Build | ATX | Lower cost, standard compatibility |
| Server/Workstation | EATX | Maximum expansion, dual CPU support |
❓ Frequently Asked Questions
Can I fit an EATX motherboard in an ATX case?
Generally no. EATX boards are wider than ATX cases can accommodate. Always check your case specifications for maximum motherboard dimensions before purchasing.
Is EATX overkill for gaming?
For most gaming scenarios, yes. ATX provides enough PCIe slots and RAM capacity for gaming PCs. EATX makes sense for gaming only if you plan multi-GPU setups or extreme overclocking.
Do EATX motherboards require more power?
Not necessarily more power, but often more power connectors. Many EATX boards need dual 8-pin CPU power connections and benefit from higher-wattage PSUs (750W+) due to their target use cases.
Are there size variations within EATX?
Yes. Unlike ATX’s strict standardization, EATX dimensions can vary. Some boards exceed the standard 13-inch width, so always verify compatibility with your specific case model.
Which form factor offers better upgrade potential?
EATX typically offers more upgrade potential with additional RAM slots, PCIe slots, and expansion options. However, ATX still provides adequate upgrade paths for most users’ needs.
Can I use ATX components with an EATX motherboard?
Yes, EATX is backward compatible with ATX components. Your RAM, CPU, GPU, and other parts will work the same way—you’ll just have more slots and connections available.
• Wikipedia: ATX Standard Details
• Intel ATX Specification Guide
• PC Part Picker: Compatibility Checker
The choice between ATX and EATX ultimately depends on your specific needs and budget. ATX remains the sweet spot for most builders—offering excellent features, wide compatibility, and reasonable pricing. EATX serves those who need maximum expansion capabilities and don’t mind the additional cost and case requirements.
Before making your decision, consider your current needs, future upgrade plans, and budget constraints. Both form factors will serve you well when matched to the right use case.