A technician is building a custom CAD workstation with a high-end graphics card.

For the highest possible stability, the best power-supply choice is a redundant power supply. In CompTIA A+ Core 1 (220-1201) hardware concepts, redundant PSUs are used in systems where uptime and reliability are critical. A redundant PSU configuration typically includes two power supply units operating together (often in a hot-swappable bay). If one PSU fails, the other continues supplying power, allowing the workstation to remain operational and preventing unexpected shutdowns that could interrupt CAD work or corrupt data. This directly matches the requirement for maximum stability.

A UPS improves resilience to power loss and brownouts by providing battery backup and line conditioning, but it is not a power supply type and doesn’t protect against the PSU itself failing. A surge protector helps guard against voltage spikes, but it also does not ensure system operation if the PSU fails. A modular PSU mainly improves cable management and airflow by allowing detachable cables; it can be convenient and neat, but it does not inherently increase stability compared with redundancy. Therefore, the most stability-focused PSU option is Redundant.