Power supplies. Now, with more wattage?!

April 13, 2004 3:44 AM

Computer Power Supplies: Why are they suddenly offering so much wattage?

Okay ... my LAST computer question as I assemble my new Athlon64 box.

I pretty much thought that 300 watts was as much as any home user would realistically need -- and that 300 was overkill at that. Yet, now I'm seeing them creep up to the 500 watt range. So, what's going on that I haven't noticed? What's sucking more power than had hitherto been needed? Are the big ol' graphics cards and new processors taking that much juice?

I'm hoping I can get by with the spare 300 watt PS I have now. Guess I'll know in a day or two. I'm really not wild about stressing my outlets more than necessary; don't wanna start popping fuses.

Any rules of thumb to guide me here?

posted by RavinDave to Computers & Internet (18 answers total)

Firstly, the output rating is the maximum. If your system uses 250W, it'll use it on a 300W PSU and on a 500W PSU.

Systems do pull a lot more power these days, mainly due to increase in usage in CPUs and video cards. Try the 300W, chances are it'll work if you're not doing anything too wild. If you encounter stability problems, chances are it's your PSU though.
posted by fvw at 3:57 AM on April 13, 2004

During my recent adventures with power supplies, I found that my system (a lowly 770Mhz AMD system with three hard drives and two cd drives) would run on a 250W PSU but a 230W PSU gave up and told me to piss off.

Might explain why my 250W was a bit tempermental at times but no works fine in a stripped down machine I'm running.

That said, this weekend I bought a new 400W PSU for £20 retail...
posted by twine42 at 4:14 AM on April 13, 2004

Response by poster: Thanx for the help (in this and the other thread).

I'll be running a pretty basic system:

ASUS K8V-DELUXE VIA K8T800 SATA, FWR, SC
AMD ATHLON64 - 3000+
512 DDR PC-3200
ATI RADEON 9600SE AGP 128MB TV-O, DVI
Floppy
80 Gig HD (Data)
20 Gig HD (Key programs)
CD/Burner
DVD Player
Zip Drive (100MB)

Again, I'm less concerned about buying a new PS (they're cheap) than I am stressing the ancient circuitry in my home. Maybe fretting over nothing.
posted by RavinDave at 4:17 AM on April 13, 2004

Other reasons:

While I'm not into case modding, I'm also not turned off by it. I've been building my new system (350w and thinking of bumping it to 400w) for the past few months and I suspect that part of the reason behind wattage increases comes from all the extra lights, fans, etc. that are now almost standard, at least where I shop. i.e. 4 fans can suck up 100 w

Additionally, both USB and Firewire ports are capable of delivering power to peripherals (which in turn might or might not self-powered). Since these ports can take a large number of devices at once, that right there is another good reason to increase wattage. I can have 10 or more USB devices connected to my home computer at once. Most don't draw power from the PC, but it could well be the opposite.

/Knows very little about hardware wattage consumption
posted by magullo at 4:20 AM on April 13, 2004

RavinDave: That's quite a lot of stuff. And Athlon64s aren't ilghtweight either. I doubt a 300Watter will pull booting all that. As said, the system will use what it uses, no matter what PSU is in between (well, unless that PSU can't give it what it requires).
posted by fvw at 4:34 AM on April 13, 2004

Here's a rough power usage guide:

Processor = 50-110 Watts
MotherBoard = 25-40 Watts
Memory = 10 Watts per 128MB
AGP Video Card = 30-50 Watts
IDE-Hard Drive 10-30 Watts
Floppy Drive = 5 Watts
CD-ROM = 10 – 25 Watts
DVD-ROM = 10 – 25 Watts
CD-RW = 10 – 25 Watts
Case/Processor Fans = 3 Watts
PCI 10/100 Nic = 4 Watts
PCI Sound Card = 5 Watts
PCI Modem = 3 Watts
USB Devices = 5 Watts
Firewire Devices = 8 Watts
posted by Tenuki at 4:38 AM on April 13, 2004

3 or 4 hard disk drives powering up simultaneously, along with anything else, is enough to tax any wimpy 300w power supply.
posted by crunchland at 4:54 AM on April 13, 2004

If you've got dodgy power – hell even if you didn’t, I’d recommend putting a UPS between your computer and the outlet. It can help prevent any damage to your computer if it suddenly requires more power than your outlet can handle immediately. But only plug your computer itself into the UPS nothing else.
posted by Tenuki at 5:12 AM on April 13, 2004

I recommend more power than you need. it's better to have too much than too little, right? a quick look on ebay shows that you can get a nice 500w supply for about $20-25.
posted by mcsweetie at 6:03 AM on April 13, 2004

I'd recommend buying a quality power supply over a super-duper-look-at-the-huge-number high-wattage power supply. Not all power supplies are built equally. Many of the generic cheap ones have huge fluctuations in voltage levels which can make your system unstable at best or harm your equipment at worst. Go for a brand name like Antec or ThermalTake. This link to a review of multiple power supplies should get you on the way to a decent unit.

Contrary to popular belief about CPU speed and all the rest, the power supply and RAM are probably the two most quality sensitive items in a computer. Skimp on either and you may very well regret it.
posted by yangwar at 6:26 AM on April 13, 2004

yangwar preaches the truth: no skimping on power or RAM. A no-name generic (basically, anything not mentioned in that AnandTech article or a few other names like Seasonic or Nexus) 550W power supply will supply a lot less good wattage than a top-of-the-line 300W or 400W power supply. As for ram, get either Crucial, Mushkin, or Corsair. There are NO other options if you want a stable system, and they all offer no-hassle lifetime warranties on their RAM.
posted by zsazsa at 6:53 AM on April 13, 2004

RavinDave, my specs are as follows:

AMD 64 3200+
ASUS K8V Deluxe
Corsair XMS PC3200 512MB
Samsung 160GB SATA
Maxtor 40GB PATA (Old backup HD)
Samsung Floppy Drive
HP CDRW
Sapphire ATI 9600 256MB
Antec True380W-S PSU
Antec Sonata case

From what I've read up on AMD 64s, you need a minimum of 300Ws to make it tick, and if you're going to be using a "modern" video card, and more than 1 harddrive, you'll need more than 300Ws. AMD 64 needs a power supply that supports the Intel P4 4 pin 12V ATX connector, without it the system won't boot up. The system in fact needs really stable rails to work properly. My suggestion is to get a good name brand 400W PSU given what you intend to run.
posted by riffola at 7:16 AM on April 13, 2004

In almost all of the computers I've had in the last couple of years, it's always the power supply fan that seems to go first. Next is the CPU fan.
posted by crunchland at 7:54 AM on April 13, 2004

Antec True380W-S PSU
Antec Sonata case

Drool... I've been lusting after these two items even since the Ars Technica review of the Sonata case. I just need to be able to justify them... The quiet PSU I can handle because I've got an aircraft engine in my current case. But a piano-black case with bright blue LED's, rubber grommets insulating all screws, and an extra 120mm fan in the back...? My inability to spend money on myself just can't handle that.

Sorry to derail the thread a bit there... As other posters have said, don't skimp on the power.
posted by humuhumu at 8:03 AM on April 13, 2004

I had mysterious and frustrating stability problems with my new computer until, after much research, I upgraded the PSU. It seems that the wattage rating doesn't tell the whole story. There are actually 3 separate power systems, 3V, 5V, and 12V, each of which have to supply enough wattage to your components. In addition, newer CPUs ( pentium IV for example) not only take more power, but also run on 12V while older ones ran on 5 V. So, older PSUs are likely to be inadequate on the 12V line to power newer computers, even if their overall wattage looks sufficient.
From experience, I also strongly recommend spending a bit more for a quality power supply.
Further details
posted by Zetetics at 8:12 AM on April 13, 2004

Sorry to derail a bit more:

humuhumu, if you check fatwallet.com, there are a bunch of threads about Sonata deals, you can pick one up for about $60 or $70 after rebates. Btw the blue LEDs are *bright* and I don't use them at all! Love the case though! If you don't need firewire, the Antec SLK3700-BQE is a better quieter and cooler case.
posted by riffola at 9:19 AM on April 13, 2004

Thanks for those, riffola. Unfortunately, I'm in the UK so I think shipping rates will cut those bargains out. However, I will be in the US over the summer, so maybe I can bring one back... thanks for the tip about the 3700 - I already have a firewire card, so that's not so important. Might be worth a look. Has a lower rated PSU though, doesn't it?
posted by humuhumu at 5:40 AM on April 14, 2004

The PSU is lower rated, but I believe you can pick a BQE without one for less money than one with it. That way you get to pick your own PSU.
posted by riffola at 7:57 PM on April 14, 2004