24 pin Amiga 3000T power connector at the motherboard.
The Amiga 3000T (Tower) is a 32-bit Commodore workstation introduced in 1990 that houses an internal AT-style switching power supply connected to the motherboard via a proprietary 24-pin header. Unlike the desktop Amiga 3000, which uses a 15-pin connector, the tower variant expands the pin count to accommodate multiple parallel +5 V and ground lines, two +12 V lines, and two Amiga-specific signals not found on standard PC power connectors. The connector carries the TICK signal, a 50/60 Hz square wave derived from the mains frequency and used for video synchronisation, as well as the FAIL power-good signal that must be asserted before the system will boot.
| Pin | Name |
|---|---|
| 1 | TICK |
| 2 | -12V |
| 3 | -5V |
| 4 | GND |
| 5 | GND |
| 6 | GND |
| 7 | GND |
| 8 | GND |
| 9 | +5V |
| 10 | +5V |
| 11 | +5V |
| 12 | +5V |
| 13 | FAIL |
| 14 | +12V |
| 15 | +12V |
| 16 | +5V USER |
| 17 | GND |
| 18 | GND |
| 19 | GND |
| 20 | GND |
| 21 | +5V |
| 22 | +5V |
| 23 | +5V |
| 24 | +5V |
Signals
- TICK — 50/60 Hz square wave derived from mains frequency; used by the Amiga chipset for video synchronisation. Standard ATX power supplies do not provide this signal. When fitting a replacement ATX unit, jumper J350 on the A3000T motherboard must be moved from the TICK position to VSYNC so the system uses vertical sync instead.
- -12V — Negative 12 V supply rail.
- -5V — Negative 5 V supply rail.
- GND — DC return / ground (pins 4–8 and 17–20); multiple pins are paralleled to reduce impedance for the high-current +5 V supply.
- +5V — Main positive 5 V supply (pins 9–12 and 21–24); eight pins are paralleled to handle the system’s primary current demand.
- FAIL — Power-good signal (active-high) indicating that all output rails are stable. The A3000T will not boot unless FAIL is asserted. When using an ATX replacement PSU, the ATX PWR_OK signal (pin 8 on the ATX connector) must be routed to this pin.
- +12V — Positive 12 V supply (pins 14–15); two pins are paralleled.
- +5V USER — Auxiliary +5 V supply intended for user-expansion purposes, separate from the main +5 V rail.
Notes
- This is an internal motherboard power header, not an external PSU connector; the power supply is housed within the A3000T tower chassis.
- The TICK and FAIL signals are Amiga-specific and are not present on standard PC ATX power supplies. Any PSU substitution requires adapting both signals: connect ATX PWR_OK to FAIL, and move J350 to the VSYNC position to replace the missing TICK.
- The pin assignments are confirmed by the Amiga A3000T system schematics (Rev. 1.38, derived from original Commodore documents) and cross-referenced with the Amiga 3000+ System Specification (Commodore, July 1991).