ATX Motherboard Power - 24 Pin - Compaq/HP

Compaq and HP proprietary 24-pin motherboard power connectors: same Molex Mini-Fit Jr housing as standard ATX but with non-standard, incompatible signal assignments.

Updated:

24 pin MOLEX 44206-0007 connector at the power supply cable 24 pin power connector at the power supply cable

ATX Motherboard Power - 24 Pin - Compaq/HP – 24-pin connector 24 pin MOLEX 39-01-2240 or equivalent connector at the cable.

Compaq and HP each fielded proprietary 24-pin motherboard power connectors during the late 1990s to early 2000s (Pentium II through early Pentium 4 era) that share the same Molex Mini-Fit Jr housing as the standard ATX 2.x 24-pin connector but carry fundamentally different signal assignments. The Compaq 24-pin variant, documented in service reference manual 133756-004, replaces the standard ATX −12V position with a Fan CMD signal and adds a Fan Sink pin, whilst its power-on control signal (ON/STBY) is active-HIGH — the opposite of the active-LOW PS_ON# in standard ATX. The HP Vectra VL5 Series 5 and VL6 24-pin connectors assign PwrGood at pin 1, multiple +5V rails across pins 3–7, +3.3V across pins 8–12, and a Remote_On signal at pin 13, a layout wholly unlike ATX despite identical physical form. Connecting a standard ATX power supply to these boards, or vice versa, will immediately damage or destroy both the power supply and the motherboard.

ColorPinNameDescriptionColorPinNameDescription
orange1+3.3VPower +3.3Vorange13+3.3VPower +3.3V
orange2+3.3VPower +3.3Vblue14-12VPower -12V
black3RTNGroundblack15RTNGround
red4+5VPower +5V16On/StbyRemote Power ON/OFF
black5RTNGroundblack17RTNGround
red6+5VPower +5Vblack18RTN / (R/S)Ground
grey7aux RTNGroundblack19RTNGround
8orange20+3.3VPower +3.3V
purple9+5V Aux+5V Standbyred21+5VPower +5V
yellow10+12VPower +12Vred22+5VPower +5V
pink11+3.3V AuxPower +3.3Vorange23+3.3V R/SPower +3.3V
red12FAN CMDFAN Powerlight blue24Fan SinkFan Sink

Notes

  • The Molex 39-01-2240 (24-position Mini-Fit Jr) housing is physically identical to that used by the standard ATX 24-pin connector; the two are mechanically interchangeable but electrically incompatible.
  • The Compaq 24-pin pinout is documented in Compaq service reference manual 133756-004 (Appendix A, section A-9). It covers full-tower Deskpro EP/EN systems and differs from the Compaq 14-pin SFF variant (Molex 39-01-2140) used in Small Form Factor models.
  • The HP Vectra VL5 Series 5 and VL6 24-pin connector carries an entirely different signal map: PwrGood at pin 1, VSTDBY at pin 2, +5V across pins 3–7, +3.3V across pins 8–12, Remote_On at pin 13, −5V at pin 14, −12V at pin 15, +12V at pin 16, and ground on pins 17–24.
  • The Compaq ON/STBY control signal (pin 16) is active-HIGH: the PSU is commanded on by driving the pin high. Standard ATX PS_ON# is active-LOW; bridging a Compaq PSU to a standard ATX motherboard without a signal inverter will prevent power-on or damage hardware.
  • Fan CMD (pin 12) and Fan Sink (pin 24) are Compaq-specific control signals that replace the −12V and other standard ATX positions; they have no equivalent in the ATX 2.x specification.
  • Do not attempt to connect a standard ATX power supply to a Compaq or HP Vectra motherboard with this connector, or vice versa; doing so can immediately destroy both units.

Signals

  • +3.3V — 3.3 V supply rail; appears on multiple pins (1, 2, 13, 20).
  • +5V — 5 V supply rail; appears on multiple pins (4, 6, 21, 22).
  • +12V — 12 V supply rail (pin 10).
  • -12V — Negative 12 V supply rail (pin 14); present on the Compaq 24-pin variant.
  • +5V Aux — 5 V standby rail (pin 9); remains live when the system is in standby or soft-off state.
  • +3.3V Aux — Auxiliary 3.3 V supply (pin 11).
  • +3.3V R/S — 3.3 V remote sense line (pin 23); used by the PSU to regulate the 3.3 V rail accurately at the point of load.
  • RTN — Return (ground) reference for the supply rails; appears on multiple pins (3, 5, 7, 15, 17, 18, 19).
  • RTN / (R/S) — Ground pin that may double as the 3.3 V remote sense return depending on the specific Compaq PSU variant (pin 18).
  • On/Stby — Compaq proprietary power-on control signal (pin 16); active-HIGH, commanding the PSU to switch on when driven high. This is the functional equivalent of ATX PS_ON# but with inverted polarity.
  • FAN CMD — Fan command signal (pin 12); Compaq-specific control output used to regulate fan speed; occupies the position that carries −12V in standard ATX.
  • Fan Sink — Fan sink signal (pin 24); Compaq-specific signal associated with thermal/fan management; has no standard ATX equivalent.

References

Category:Power Supply Connectors