Power supply (PSU) concerns

By truffles · 267 replies
Mar 5, 2002
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  1. Eric Legge

    Eric Legge TS Rookie Posts: 132

  2. Malladine

    Malladine TS Rookie Posts: 20

  3. Nic

    Nic TechSpot Paladin Posts: 1,549

    Don't buy a cheap PSU, as you'll regret it. If it ever fails it will likely take out many of your other components along with it. I've seen this happen at least 3 times in the past.

    Cheap PSU's don't always have good output protection (over-voltage, over-current, etc.) to protect attached devices. If you buy anything other than a respectable brand, then you might be ok, or you might end up regreting it.

    Good electronics design and quality components cost money, so cheapies are an extra risk your valuable equipment doesn't need.

    Also, the PSU wattage rating is not the power that is supplied to the load, which is often considerably less, so don't go by simple wattage ratings and try to read some of the reviews that others have kindly provided links for.:cool:
  4. Malladine

    Malladine TS Rookie Posts: 20

    Indeed Nic. Given that the power supply - ahem - supplies power to the entire system, one could say that it is the most important choice for a builder to make.
  5. Nic

    Nic TechSpot Paladin Posts: 1,549

    I agree, followed closely by a good mainboard.

    I once lost 2 hard drives, a CDR drive, and a DVDROM to a cheap PSU that appeared to be working, but was producing voltage spikes on start-up. I didn't discover the problem till it was too late, and had to replace all the drives and the PSU. It worked out to be a costly mistake, and I lost all my data into the bargain as it wasn't backed-up. I now ONLY use respectable brands like Enermax.

    There are some good PSUs around that are reasonably priced, but cheap ones should always be avoided. The better ones tend to be quite heavy, whereas cheapies are relatively light. While this is not the recommended way to tell if a PSU is good or not, you'll find that ALL the good ones ARE heavy. Cheapies are designed to be low cost and that inevitably means fewer components and low weight to save on shipping costs.

    All the latest top spec CPUs (and GPUs) now require better power regulation, as well as lots of power, and this will become even more important as time goes on.
  6. StormBringer

    StormBringer TS Maniac Posts: 2,244

  7. consie89

    consie89 Banned Posts: 47

    Nice to see an old latin enemy bringing itself down :)
  8. lowman

    lowman TS Rookie Posts: 380

    Antec is my PSU of choice...quality stuff, and they really stand behind their products...I run a 550W unit, but it's a more robust system I am powering...
  9. Mattz

    Mattz TS Rookie

    I have a A7S333 MoBo and Amd 2.0GHZXP WITH 1G MEMORY what kind of psu watts should I use
  10. Vehementi

    Vehementi TechSpot Paladin Posts: 2,704

    How many hard drives and case fans do you have? I would reccomend a quality 350W PSU unless you have in excess of like 5 hard drives and fans.
  11. Rory7

    Rory7 TS Rookie Posts: 119

    I have a 300watt power supply, im also planning on buying a case fan and some more RAM. Do you think my wattage is cutting it close a bit? (System specs in profile)

  12. Ollie30001

    Ollie30001 TS Rookie Posts: 144

    Hey, just a slight....."wondering".....a got this pc (one im using now) about 3 months ago..it was sed to be in the high range group of pcs and all, the specs are at the bottom bit of the page (were u put ur sig and that) and i was wondering why it came with such a low power suply wattage and was wondering if i got it wrong.....i looked on the side of the psu and it ses something like "max out: 250watt" is there another way to find out what it is? anyway...as u can see my comp has one HDD some network card in a pci socked, a radeon 9200 128 mb ( :( ) 3000+ AMD Athlon xp and 512MB of RAM.

    im looking to upgrading my graphics card to something way better that what i have now.....i was thinking the Radeon 9800 256mb and was wondering if the power suply would cope wiv it.....dunno what make it is....soooo....any help would be nice.....
  13. Ollie30001

    Ollie30001 TS Rookie Posts: 144

    Yo, me agen...ive been looking around and just decided to get a new psu....how hard can it be to plug in a few wires...anyway, i come across this site...seems to be good prices.....but what one should i go for....im not looking on paying £100 for a psu...so something around £50 to £65 will be more like it for me......

    Heres the link:

    http://www.planetmicro.co.uk/result...06&sort=low&title=Power Supply Units&images=1
  14. damian korea

    damian korea TS Rookie

    Power Problems

    I have 450mhz
    win xp
    3dfx 8mb video
    tv 2000 video in
    2 ethernet cards
    Hoontech (Professional sound soundcard)
    2 usb 2.0
    (All except for 2 ISA slots are full)

    I upgraded my computer a bit (installed RAM and new cards).
    When I turned the power on, the BIOS screen worked as normally exept that I heard sound coming from the speakers (like an alarm sound) for 10 seconds. Then the computer shutdown and smoke came out from the PC.
    What happened and what could the extent of damage be?
  15. poertner_1274

    poertner_1274 secroF laicepS topShceT Posts: 4,172

    I would definately say you are way overtaxing that 250watt PSU, and if finally crapped out with all that stuff hooked up to it. I'd simply suggest getting a new 400watt Enermax or something similar, you will be happy with a name brand PSU, instead of a generic one.

    :wave:Welcome to TechSpot:wave:
  16. The Best Alias

    The Best Alias TS Rookie Posts: 113

    Smoke is never a good sign. I'd say almost certainly your power supply has failed. If it's a good PS with adequate protection, it will shut itself off before anything catastropic happens. Some failures result in the voltage going down which won't harm your PC. Unfortunately, most PS failures are from a rectifier failure or more commonly a voltage regulator failure. If a rectifier fails, AC gets loose in a DC circuit and you've most likely lost everything. If a regulator fails, the DC voltage becomes irregular and the computer will start acting funny, ie shutting itself off for no reason. Regulator malfunctions tend to get worse over time and are usually caused by overloading the power supply.

    The only way to tell the extent of the dammage is to get a new power supply and power up one thang at a time. If what you do on a your PC is important to you, you will invest in a good power supply. I too sing the praise of Enermax.

    A side note about overloading power supplys. If you are adding a new piece of hardware and you have to use one of those power splitters that they usually package with drives and fans, chances are you are overloading a circuit. there is a reason a 250W only has 4 power drops and a 550W has a kazillion. Those little splitter are like asking for trouble. Adding another case fan may be done with all the best intentions in the world, but it can be the straw that broke the camel's back too.
  17. joshuaCHedges

    joshuaCHedges TS Rookie

    Okay> I think we've thrashed this subject to death...

    ...but I just thought having read through the posts that I would add my 6 pence worth.

    As a hardware engineer and looking at this from a large corporation server point of view.

    The mainboard can take upwards of 30w. 30w being about the minimum of a basic ATX form factor (ff). This will rise on the later ones, although the smaller ff boards have been designed with power consumption reduction in mind. Also mainboard that include a mezzanine layer or riser boards will take more.
    This does not count the RAM or CPU. Ram is rated at 10w per 128MB and that is the calculation I use for Xeon Dual & Multi-processor server machines using 100 or 133MHz SDRAM DIMM modules and, of course goes up with frequency, although voltage comes down a little. A PC3200 runs at 400MHz DDR & 2.7v, with this and other design enhancments the calculation would still be about the same.
    CPU's are quite power hungry. Intel have got some better models out for the laptop, like the Centrino and Mendocino, but they are normally classed, for a single component, as the largest uses of power, with the Intel P4 normally using more power than the AMD Athlon. Compare a 3.4GHz Intel 90nm P4 and an AMD Athlon 90nm 64bit 3.5GHz and the power consumption is about double in the Intel chip. I would say to allow up to 100w (though see below), with the newest P4 600 series, even though they have 125million transistors and double the ATC L2 cache to 2MB, actually using less power. The hyperthreading technology in the Intel CPU uses about 10% more power but for shorter bursts as it finishes tasks quicker.
    The calculation is (Total Capacitance*frequency*(voltage²))/2, hence a 3.2GHz Intel P4 'C' CPU using 1.5volts internally will consume ≈ 70w whereas the Intel P4 mobile 715 running at 2GHz consumes only ≈ 16w. The 64bit AMD Athlon FX-55 running at 1.5v internally consumes ≈104w and the latest Pentium mobile CPU core code named 'dothan', this is in the 'sonoma' CPU with a 90nm process, 2MB of L2 cache and a speed of 2.13GHz (Pentium M770) uses only about 27w. There is another techonlogy that I have not investigated, but this is called 'Transmeta Crusoe' and is based on allowing the ouyter layer functions of a CPU to be carried out in software. The CPU consumes a lot less power and is well suited for smalled portable devices. a 700MHz with a core voltage of 1.6v uses only 3w. It is x86 compatible.

    So a basic 30w consumption mainboard with 1GB RAM and a 3GHz CPU could be using 175w


    5w for the floppy (if you still have one)
    25w for a 50x CD-ROM or 10x DVD-ROM
    30w for a 4x AGP card (beware here some cards can consume vast amounts of power. An ATI Radeon 9700 Pro GPU uses 45w. Some have 2 molex power sockets on them, so use more power. Those normally recommend at least a 350watt power supply.
    PCI cards (33.2MHz x 32bit) use about 5w each
    IDE 5400 drive = 10w IDE 7200rpm = 15w, but all harddrives use a lot more power when they are spining up and this should be allowed for. A 7200rpm will use up to 30w and a 10,000rpm up to 40w. Having said that the newer models of drive are better at managing power useage and may be slightly less, but err on the side of caution.
    SCSI harddrives use more power 7200=25w, 10,000=40w and more during spinup.
    It is always sensible to go for a good model. If you buy a decent case you should get a decent PSU, but you can always do better and as has been said a few times, branded models are going to be better. It makes sense logically. The company is proud of there equipment and so brands it.
    I would go for a minimum of 350w today and normally 400w
    And better models are quieter, have a cleaner power output, are less likely to have problems with the Rectifier. If that goes wrong there is no telling what damage you could do to your computer as AC power could get through to your components.

    Have fun.
  18. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    heck I have a 600W supply in the computer I built.
  19. Finchy

    Finchy TS Rookie Posts: 353

    I think we need some suggestions as to bad PSU brands, the ones to stick clear of, so if you don't have enough money to buy a high quality PSU, you know which of cheapos you shouldn't get.
  20. agoodies

    agoodies TS Rookie

    In the Process

    I am sort of a newcomer as far as building my own PC. I have just order my motherboard,RAM,Processor,heatsink/Fan and my powersupply.

    Asus K8V SE Deluxe Socket 754 ATX Motherboard
    AMD Athlon 64 3200+ Processor and
    Ultra 512MB DDR Memory
    550w diabloTek Powersupply

    I also bought a case that came with a 400w power supply.(Forgot the power supply was in there already). I was just wondering if anyone could tell me if the 550w DiabloTek PSU was a little to much. Should I stick with the 400w PSU that came with my case. Any help would be much appreciated.

  21. poertner_1274

    poertner_1274 secroF laicepS topShceT Posts: 4,172

    Well it all depends on what you are planning on doing in the future. If you want to add more components, then it might be a good idea to keep the 550. Also if the PSU that came with the case isn't a branded one (quality) then you might want to just go ahead and use the 550 as well.

    :wave:Welcome to TechSpot:wave:
  22. agoodies

    agoodies TS Rookie

    Ok,is 550 to much for what I have right now?? Will it be to much power if I decide not to add anymore components. I just dont want to overpower my PC and waste all this money.

  23. Finchy

    Finchy TS Rookie Posts: 353

    The 550 should last a good few years of buying top-range hardware, whichyou probably won't be doing much. It's more than adaquete.
  24. nucleardreams

    nucleardreams TS Rookie Posts: 68

    Below is a link to AMD's guide for building a PC system. Starting on page 9, it describes how to calculate the system wattage thats right for your components. Theres even a worksheet to help you through your calculations.
    Don't forget, alot of USB devices pull power directly from your PC, so you'll have to factor them in as well.
  25. vibing_v

    vibing_v TS Rookie

    PSU questions!

    After months of having my computer freeze on me (ie while watching video files or playing games) and asking around I'm fairly certain the problem is my PSU. Given that it is now 4 years old and that the problems started when I updated to a P4 this makes sense.

    So I'm looking at PSU's to buy. My current set up (P4 1.8Ghz, AGP geforce 3ti - more details in profile) I'm sure doesn't require a huge amount of power, but I'm looking to upgrade within the next few months to an Athlon64 3000+ or higher, & leadtek 6600GT pci-x.

    I want to invest in a reliable PSU, but I see no point in buying one now and another one a few months down the road. So my question is, will I have any problems using a higher range PSU on my current system? For example, my main concern is if I buy a PCI-X ready PSU to use with my current AGP setup will it cause any problems having a PCI power connector just hanging around not attached to anything?

    I have my eye on this one for now: http://www.ncix.com/products/index.php?sku=13569 :D

    Any feedback would be greatly appreciated. :)

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