AT 400W PSU (Original) with P8 and P9 Connectors Genuine AT PSU
Rare, genuine AT power supply unit delivering reliable power for legacy systems built on AT technology. Specifically designed for vintage computing applications.
Compatible Systems
Vintage Home Computers
& Workstations
Hard Drive
Storage Enclosures
Shopping Mall Kiosks
& POS Terminals
Arcade &
Entertainment Machines
Legacy Industrial
Control Platforms
Manufacturing Plant
Control Systems
Key Features
P8 & P9 ConnectorsStandard 6-pin flat white motherboard connectors (AT standard)
400W Output PowerHigher output than our 300W AT PSU
Molex, SATA & Floppy4x Molex, 2x SATA, 1x Floppy connectors
Remote ON/OFF SwitchConvenient system power control
80mm Cooling FanReliable airflow for continuous operation
2-Year Warranty1 year standard + 1 year free extended
Important Remarks
Please read before installation:
- P8 and P9 connectors must be plugged in so the black wires sit side by side, together in the centre.
- Some systems without motherboards do not require the P8 & P9 connectors, which can be left unused.
- Some systems do not require the On/Off switch — it can be left switched ON and tied up safely inside the machine.
- Supplied with a large latching switch suitable for most AT systems. It is removable and can be replaced (terminal block size: 9x0.6mm). Check the diagram on the PSU for correct wiring — an incorrect connection will damage the PSU.
- The P10 connector is not fitted as standard. It is available as an option in two versions — see the P10 section below and make sure you select the correct one.
Optional P10 Connector — Choose the Correct Type
Some AT systems need a third 6-pin connector, called P10, in addition to P8 & P9. It has 3 black wires plus 3 coloured wires, and there are two different versions:
P10 with Orange Wires — +3.3V Most common
3 black wires (ground) + 3 orange wires (+3.3V). This is the version most AT systems with a P10 connector use.
P10 with Red Wires — +5V Rare
3 black wires (ground) + 3 red wires (+5V). Rarely found on AT PSUs — only choose this if your original P10 has red wires.
Check your original PSU before ordering:
- Look at the wire colours on your old PSU's P10 connector: orange = +3.3V, red = +5V. Select the matching P10 option.
- The two versions plug into the same socket but supply different voltages. Fitting the wrong one can damage your motherboard or system.
- If your old PSU only has P8 & P9 (no third 6-pin connector), you do not need a P10 option.
- Not sure? Contact us with a photo of your old PSU's connectors and we will confirm which one you need.
Watch: P8 & P9 Connector Guide
Not sure if this is the right PSU? Use the
Compatibility List tab to search for your model, or
contact us with your old PSU model number and a photo — we're happy to help find the right match.
