Choosing a Decent PSU for my future 7800 GS

By rmdl51 ยท 5 replies
Jul 15, 2006
  1. Hello Guys! ok you are the experts on PSU's I'm not , so I would appreciate your opinions and suggestions here, first, what is the most important thing, the 12V rail or the total wattage? it's ok to get a 350w PSU that have 20A on the 12V rail o not?, so a PSU with two 14Amp 12V rails, means that has 28Amps on the 12v rail? for instance, what do you think of this:
    Power Supply Specification:
    Maximum output:
    Less than 1 ms
    Output Characteristics:
    +3.3V 32A
    +5V 40A
    +12V 24A
    -5V 0.5A
    -12V 1.0A
    +5V Standby 2.0A

    two 12v rails are better than one? or is the same having one rail with the same amount of amps, oh! almost forgot, anyone knows the reputation of the brand Enlight PSU's, thank you in advance and i hope don't drive you crazy with lots and lots of questions, I'm kind a newbie at PSU's :blush:
  2. Rage_3K_Moiz

    Rage_3K_Moiz Sith Lord Posts: 5,443   +38

    2 12V rails are usually used in most new PSUs. It's not a question of 2 or 1 rails, it just boils down to the total amps on both rails together or on the one rail. For the 7800GS, I would recommend at least 36A on two rails i.e. 18A on each rail. Enlight is not a bad brand, but I would recommend an Antec, Enermax, Fortron or Thermaltake. Where are u living. Assuming ur in the US, try this PSU out.
    It has 38A on the 12V rails so it will hande ur 7800GS with no problems.
  3. KingCody

    KingCody TS Evangelist Posts: 992   +8

    1. the 12V rail (or rails) is the most important

    2. two (or even three) 12V rails are better than one

    3. I have never heard of Enlight, so I cannot say whether they are good or bad quality. but i can say that I would not trust them simply because of how ridiculously high they rated that weak PSU. i say it is weak because they say that it's 600w, but it only has a meager 24A on the 12V rail.

    just as a comparison... Antec's biggest/most powerful PSU is the NeoPower NeoHE 550. it has three 18A 12V rails, which results is a 54A 12V rail. and antec rates that PSU at 550w.

    Antec, Enermax, Fortron, SeaSonic, and PCP&C are all good reputible brands. I have read good things about thermaltake's higher end PSUs are good, but they over-rate their usuable wattage, so I personally wouldn't buy one.

    Antec is my personal favorite. they use realistic power ratings, provide very stable voltage and consistant amperage, and they have reliable protection circuitry. I have an Antec TruePowerII 380W PSU (12v@32A via two 16A rails)

    hope this helps :)
  4. Mirob

    Mirob TechSpot Paladin Posts: 478

    You can't necessarily just add the rails together to get the maximum total output. Often the better quality brands will give the total output. Look at this FSP 700 watt PSU:

    It has four 15 amp 12 volt rails, that totals 4 x 15a x 12v = 720 watts. It can't run all rails at maximum and it notes that on the sticker showing 680 watts maximum combined power output.

    This one would work well for you,

    It is better to have just one rail because if the GPU needs power and the CPU is not using much it is avalible. With two rails the GPU or CPU may overload it's smaller, single rail. It often said single rails are preferred for Pentium 4's since they can load the 12 volt rail with high current burst. The move to multiple rails is just so manufactures can use more of cheaper parts, rather than a few expensive high quality parts. The Zippy 700 watt PSU has a single 46 amp 12 volt rail--it's the King Daddy of PSUs, a overclockers dream.

    To learn more about PSU's you can read David Hammocks's posts at Hardfourm and Extreme Overclocking Fourms. They are full of usefull infromation.
  5. rmdl51

    rmdl51 TS Maniac Topic Starter Posts: 244

    Thank you all! Good information, I'll choose one of those you recommend, before I knew I wrongly pick the ones with higher wattage, when i bought my PC case it cames with a cheap PSU, so i build my system and turned on and used it for a couple of weeks I leave it turned on for all the night long and next day it was off, no wonder why I just open the case took out the PSU open it and it was completely burnt, lucky me it didn't burn the whole system, so this was 300w (i don't even know what was on the 12v rail :p )
    so i went to the store and pick something between 400-450w without verifying any other specs :knock: , the price, well 39.99 what could I spect right? that is the PSU i have right know and has only 14A on 1 - 12v rail, well i learned the hard way how important is the PSU, again Thanks and appreciate all the information you provide to make a smarter choise on PSU this time!! :wave:
  6. KingCody

    KingCody TS Evangelist Posts: 992   +8

    mirob raises a good point about single vs. dual rail.

    dual rails provide cleaner power by separating the CPU power from the peripheral's power.

    extreme overclockers will want to use a high quality single rail PSU when overclocking a power hungry CPU like a prescott (presc-hot ;))

    In most cases however a multi-rail PSU is can provide sufficient power to all components and an overall cleaner power output.

    as far as I know, the current ATX specification for a dual rail PSU is the +12V1 rail powers the CPU and motherboard via the ATX 24pin connector. the +12V2 rail powers the peripherals and the auxillary power connectors (the CPU 2x2 connector and the auxillary GPU connector) with this setup the CPU and GPU should get sufficient power from both rails. I could be wrong though (I'll verify it later, but right now it's lunchtime :D)
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