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Thread: Auxiliary Power Connector on 486 Motherboard

  1. #1

    Default Auxiliary Power Connector on 486 Motherboard

    A couple of years ago I picked up this late-era 486 motherboard at a Goodwill and am finally getting around to testing it.

    DSCF1013.jpg

    It has an AT auxiliary power connector. Now, I've never seen one of these on an AT board before, and I certainly don't have a PSU that has the "additional" power plug. I plugged a regular AT PSU up to the P8 & P9 connectors and got no signs of life from the board whatsoever. No video, beeps or anything. Is the auxiliary power connector required, or do I just have a dead board? Thanks for the help!

  2. #2
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    The aux connector is for 3.3V... so it may be required for that motherboard.

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    You see these connectors on HP 486/p1 and some p2 motherboards. HoJoPo is correct--they're for 3.3V.

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    What was there on a 486 board that needed 3.3v? Most boards I know of from that era did 3.3v regulation onboard. That board also has PCI slots keyed for 5V.
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    I've seen a number of Socket 5 Pentium era motherboards with the extra connector but onboard voltage converters. They worked fine without anything plugged into the aux connector, and shipped that way from the OEM. This may be a similar case, but as mentioned you should try and find the manual to confirm.

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    I've also seen this sort of connector on early boards for a backup power supply. Like Glitch says, find the manual.

  7. #7

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    Thanks everyone for the input. The board does appear to have a voltage regulator on it. I cannot find a manual or even a brand for this motherboard. However, I do believe it came out of a Gateway 2000 -- I found a thread over on VOGONS (http://www.vogons.org/viewtopic.php?f=46&t=41864 -- last picture from the bottom) where the poster had taken a picture of the interior of his Gateway P4D-66 tower, and the board looks very close to mine. Most definitely same OEM. And his auxiliary power plug was not connected. Guess I'm going to chalk this one up to a dead board. Not surprising -- there's no telling what this thing went through before and after it ended up at Goodwill!

    I have a socket 7 board I picked up with this one at the same time. I don't have very high hopes of it working either...
    Last edited by Gramcon; August 24th, 2017 at 08:34 PM.

  8. #8

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    Well, maybe the cpu is still good though.

  9. #9

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    This motherboard must need it. Strangely enough I have an ATX LGA775 Core2 motherboard that has this connector too. But it seems to work fine with just the ATX and 4 pin P4 connector. I thought it strange that this late of a motherboard would have this connector.

  10. #10

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    I have always wondered about this Aux connector. It's found on the Intel Batman (5V 60MHz Pentium board) and their early socket 5 boards. According to the manual for this board:

    "PCI 3.3 VOLT CAPABILITIES
    To maintain strict compliance with the PCI specification, the motherboard provides a connector which can be used to route 3.3 volt power to the PCI slots. The connector may be used with a separate 3.3 volt power supply or with a custom designed voltage converter."

    From what I have been able to piece together, it looks like early 5V PCI slots were supposed to supply 3.3V as well. I guess this was relaxed at some point, as they are AFAIK useless in a 5V slot. Perhaps the PCI 2.1 revision relaxed the spec. As mentioned this connector found its way into the ATX era. I tried to look up the PCI spec once but they wanted $$$ to read it. I tried to research this twice, but always end up at a loose end.

    Practically speaking, AFAIK, this is ONLY used to power the PCI slots, that don't need it anyway. There may have been a non-intel board, that allowed a 3.3V CPU to use this power source.
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