Motherboard and PSU — Hardware Planning for Local AI (Chapter 10)

GPU and CPU selection means nothing without proper supporting components. Motherboards and power supplies require careful consideration for stable AI workloads.

Motherboard Requirements

Essential motherboard features for AI workstations:

Feature	Minimum	Recommended	Notes
PCIe slots	PCIe 4.0 x16	PCIe 4.0 x16	GPU bandwidth
PCIe lanes (CPU)	16	20+	Resolved by CPU model
RAM slots	4	4	Upgrade path
RAM capacity	64GB	128GB	Model loading
M.2 slots	2	3+	Fast model storage
USB	3.2 Gen 2	4.0	Peripherals

CPU and Platform Considerations

PCIe lane allocation varies by CPU:

CPU	Total PCIe Lanes	GPU Usage	Remaining
Ryzen 5 7600X	24	16	8 (NVMe, USB)
Ryzen 9 7950X	24	16	8
Core i9-14900K	20	16	4
Threadripper 3960X	64	64	64 remaining

Single-GPU users have flexibility. Multi-GPU requires more lanes.

PSU Calculations

Calculate total system draw:

Component	Typical Load
RTX 4090	450W peak
RTX 4080	320W peak
RTX 3090	350W peak
CPU (AM5)	125W
CPU (LGA1700)	125-250W
RAM (4 sticks)	20W
Storage, fans	30W
Motherboard	50W

Single RTX 4090 build: 450 + 150 + 20 + 50 = 670W minimum Dual RTX 4090 build: 920 + 150 + 20 + 50 = 1140W minimum

Recommendation: 1000W for single high-end GPU, 1600W+ for dual configuration.

Quality Considerations

PSU quality matters more than wattage:

80+ Gold minimum for efficiency
80+ Platinum for dual-GPU systems
Brand matters: Seasonic, Corsair HX, EVGA SuperNOVA are reliable
Avoid cheap units—GPU load transients can exceed average draw

Case and Cooling

High-end GPUs require:

Minimum 3-slot clearance for RTX 3090/4090
120mm+ intake fans
Positive air pressure (more intake than exhaust)
ambient temperature under 30°C for GPU longevity