New Antec NeoHE 430W is not working with Abit AS8 motherboard. Why? 5V? ATX spec?

By stephen_le_page
Feb 5, 2006
  1. New Antec NeoHE 430W is not working with Abit AS8 motherboard. Why? 5V? ATX spec -5V?

    I want to raise the issue of ATX spec changes and backward compatibility conflicts.

    I chose to buy an Antec NeoHE 430W ATX v2.2 PSU ( to replace my dead PSU because the higher efficiency would definitely save me money on the electricity bill, and 18dBA is nice and quiet. It also claims to be "backward compatible with all ATX 12V systems". But it is definitely not working with my Abit AS8 motherboard, and I need help understanding why, and advice on if it can be made compatible somehow?

    Before I purchased the Antec PSU, I borrowed a 300W Auriga PSU ATX v2.03 ( for testing, and it works flawlessly to boot my 288W system (100% of the time, over about 8 tries) - thus showing that my only problem was with my old 430W PSU, and not anything else.
    Note that the 5VDC rail of this new Auriga PSU measures at 5.17V. (3.4% over 5V).

    With the Antec PSU installed, my system failed to boot 100% of the time (out of about 15 trials) with an amazing variety of symptoms:
    * Sometimes, it fails 0.3 seconds after booting, flashes ' 1' on the POST display, and resets after 1 second.
    * Sometimes, it fails during POST with '75', then '76', then hangs on '7F' reporting the error:
    "CPU is unworkable or has been changed. Please recheck - CPU SOFT MENU" (The CPU of course has not been changed)
    * Sometimes, it completes POST, and the OS (WinXP Pro SP2) boot process fails even before the splash screen comes up to full illumination. (When choosing to boot in Safe Mode, it hangs after the line ....\system32\config\system.)
    If one thing happens to work, something else will fail!
    Note that the 5VDC rail of this brand new Antec PSU measures at 4.90V. (2.0% below 5V).

    The only things that I can think of that might explain why my motherboard is rejecting the Antec power supply are:
    1) The 5V is too low - (unlikely because 4.90V is within spec)
    2) there is an ATX specification mismatch, perhaps because of the absence of a -5 VDC line?

    According to the hardcopy of the manual that came with my Abit AS8 Motherboard (rev 1.00, 4200-0409-01), section 1-2, "The Switching Power Supply must meet ATX 2.03 specification with ATX12V and AUX Power connectors." but, if you download this manual from, you get a newer version (rev 1.02, 4200-0409-05), in which this assertion has been removed from the manual! Nevertheless, both version of the ABIT AS8 manual shows (in section 2-4 Connectors, Header and Switches) a diagram that marks pin 18 as -5VDC.

    I also read that Antec PSUs no longer provide the -5VDC to pin 18 (of a 20 pin ATXPWR1 connector). Antec's FAQ says "The -5v rail has been removed from the Intel Standard and is no longer needed."
    Despite this, Antec still advertises the Antec NeoHE 430W ATX v2.2 PSU ( as "backward compatible with all ATX 12V systems" - which is why I thought it was ok to buy it.

    If there is no -5V DC rail, then is it really backwards compatible to previous versions of the spec?
    So what does the specification say? There seems to be some inconsistency regarding when this this -5VDC line is removed from the specification too!

    According to v2.2 (,
    * In the Revision History on page 3, the -5VDC was removed in spec v2.01 (so the Antec PSU would be backwards compatible to v2.01)
    * Section 4.5 (page 36) shows pin 20 of 24 as NC (equivalent to pin 18 of 20)

    But if you read v2.03 ( 2.03 Spec.pdf), you find:
    * In the Revision History on page 3, the only mention of -5VDC is with regard to a correction to voltage tolerances, i.e., no deletion.
    * Section 3.3.2 (page 14) "this interface incorporates standard ±5 V, ±12 V, 3.3 V, and soft-power signals."
    * Section 4.2 (page 23) shows pin 18 of 20 as -5V.
    So according to this, the Antec PSU would not be backwards compatible to v2.01 or v2.03!

    So, whether or not the Antec v2.2 product can be described as backwards compatible depends on which version of the spec you're looking at! So it may or may not be false advertising....

    What matters to me is that it isn't working with my Abit AS8 motherboard, and I doubt I'll be able to return a working product to the wholesaler that I bought it from.

    If anyone has any more theories why the PSU and motherboard are not working together, I'd love to hear from you.

    Best regards,
    Stephen Le Page

    Other spec definitions:

    My System:
    Hairong 8331A P4 ATX MidiTower with ATX-400WA power supply (dead after 15 months)
    ABIT AS8 motherboard with Intel 865 chipset (25 W)
    (BIOS Version i865PE-W83627-6A79AA1MC-18, 22 July 2005)
    Intel P4 '530' 3.0GHz LGA775 (90 W)( + CPU fan 3 W)
    ATI Radeon XpertVision 9200SE (DVI & VGA) (35 W)
    Corsair TWINX1024-3200C2 DDR SDRAM 400MHz (20 W)
    Hard Drive Maxtor DiamondMax Plus 9 200Gb SATA (25 W)
    Hard Drive Hitachi Deskstar 7K250 80GB IDE (25 W)
    DVD-RW Sony 8x DRU700 (25 W)
    CD-RW LG GCE-8520B 52x (20 W)
    Creative Soundblaster Audigy 2 Value (7 W)
    Samsung SyncMaster 710V LCD monitors (x2) (separate power supply)
    floppy drive (5 W)
    Microsoft keyboard and optical mouse (3 W)

    Total 283 W (or 288 W min according to the calculator at
  2. werty316

    werty316 TS Rookie Posts: 185

    These PSUs come with Antec's P150 and they aren't very good for relability. Many people who bought them had the PSU die on them, not work at or were unstable. I have had 2 experiences where the PSU was fixed as the warranty sticker was broken. Is th ewarranty sticker broken on yours? I suggest you contact Antec if it isn't or is. I say that the Antec NeoHE 430W is cursed.
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