PSU do i need -5v rail ?

Hi guys
For what is the -5V rail in psu used ? do i need it ?
15 answers Last reply
More about rail
  1. You may need it if you have a very old PC with ISA cards, but it probably wasn't used. http://www.smpspowersupply.com/connectors-pinouts.html and http://www.smps.us/20-to-24pin-atx.html
  2. I just watched on my motherboard
    In my ATX 20+4 pin connection to her is writen on one of 20 points -5v rail. Soo i need -5v right?
  3. Not unless your motherboard is very old and you still have ISA cards.
  4. My motherboard is GA-H55M-S2 from Gigabyte
  5. That motherboard is too new to have ISA slots. In addition, it uses a 24-pin PSU connector; newer PSUs normally don't have a wire on the -5v pin. Did you ask the question because you're getting a new PSU that doesn't have a -5v rail?
  6. yes and in user's manual of my motherboard in section (1/2 ATX_12V/ATX (2x2 12V power connector and 2x12 main power connector) is information about the 24 pin psu connector from 1 to 24 pin
    1- 3.3v
    2- 3.3v
    3- GND
    4- +5v
    5- GND
    6- +5V
    7- GND
    8- Power Good
    9- 5VSB ( stand by +5v)
    10- +12v
    11- +12v ( only for 2x12-pin ATX)
    12- 3.3v (only for 2x12-pin ATX)
    13- 3.3v
    14- -12v
    15- GND
    16- PS_ON ( soft on/off)
    17- GND
    18- GND
    19- GND
    20- -5V
    21- +5V
    22- +5V
    23- +5V (only for 2x12-pin ATX)
    24- GND (only for 2x12-pin ATX)


    In 20 there is -5V

    soo ?
  7. So it isn't used because you can't install ISA cards. Do you know what ISA cards are? They are the type of cards that were used before PCI 1.0. Does your PC work properly?
  8. I have currently i3-540 + 4gb ram and i am buying a new video card GTS 450
    And to all that i need a new psu
    soo the main question is... what will be if my psu... ups no -5v rail =)
    and 1 question about psu. Thay have filters like PFC / OVP /OCP /UVP /OLP /SCP etc

    If my psu will have only this OLP /OVP / SCP... will it be enough?

    And what about Tracer HIghlander brand with 500W with all this filters PFC / OVP /OCP /UVP /OLP /SCP should i buy it ?
  9. Do not worry about the -5Volt thing, it does not matter at all.

    Do not buy a Tracer Highlander brand PSU. You should never buy an off brand PSU, they commonly fail, taking the rest of your system to the grave with them.

    Buy an Antec, Cooler Master, Corsair, or at the cheapest (marginal) OCZ, do not go any cheaper than those brands.
  10. You don't need -5v; you would only if you had a PC older than year 2000 (and even those rarely had ISA cards).

    You definitely want a PSU with Active PFC, i.e., no 115/230v switch as found in cheap PSUs. Any quality ATX 2.01 or newer PSU will work just fine as long as it is powerful enough.

    Who manufactures the Tracer Highlander 500w and what are the specs? 500w means nothing; cheap PSUs rarely achieve their rated output while quality PSUs usually exceed it. A quality 450w PSU meets your requirements.

    Don't you have access to PSUs manufactured by Antec, Corsair, PC Power and Cooling, etc.?
  11. my budget is allmost over cause i buyed new video card and 2 gb ram
    what do you think guys about
    TAKE ME 500 SILENT 12cm [TAKZAS30889] ? cause this my budget will allow to buy
    it has OVP,OCP,OTP,SCP
    PFC avaible and 27.5a on +12v Rail

    ??
  12. Do not buy an off-brand PSU.

    Acceptable companies include Antec, Corsair, PC Power And Cooling, XFX, OCZ, and Seasonic. A cheap, generic brand power supply will almost always burn out in a short period of time, often taking the rest of the system out with it.

    If you don't have any money left, then wait until you do.
  13. hmm i decided not to buy... YET!
    but guys
    i got few questions
    Cause... I think my PSU will be enough for my configuration. Dunno if its true
    I have i3-540 and intel says it needs 73W
    The new Gts 450 that i buyed - needs 106W
    Motherboard GA-H55M-S2 Gigabyte
    2 sticks ddr3 ram
    1 HDD
    1 DW-RW
    and thats all
    My psu has on +12v rail 20A and that gives 240W

    Soo
    106+73=179+(HDD+DW-RW+ddr3x2) 40W ?? = gives around 219W right?

    Soo here are my questions

    1. How often will the CPU and GPU be at max load ? meaning that i intend to play new games on max? ( i have 1240x1024 i can do this )

    2. Are my calculations about 219W right ?

    3. Will be there a problem if my +12v rail on PSU will be used allmost at maximum? My PSU has 500W and only 240W on +12V rail
  14. no one knows ? cause i dunno should i launch this configuration or not
  15. A PSU with a single 20A on the +12V rail is not a 500W PSU. Are you sure that it doesn't have another +12V rail? If not, then it's not good enough.
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