Is 400W enough?

[flamingspinach]

My planned system has quite a bit of "extras", such as a GeForce 6800 NU, SB Audigy2 ZS, DVD+/-RW drive, and SATA HDD - will a 400-watt power supply be adequate to power the machine? Thanks.

-fs

 

[Crism]

If you could post the brand and model that would be cool. It all depends on the rails and quality of the PSU in general. Anything brand name, Antec, Enermax, etc should be ok

 

[stevty2889]

yeah, if it is a quality 400w PSU, then it will be fine. DO NOT get a cheap or generic PSU, it's asking for trouble.

EDIT: Looked at your planned system...I would definatly get a differant PSU. 18a is a bit too weak on the 12v rail, especialy for a supposed 400w. My 350w enermax had 26a on the 12v rail. Your video card, cpu, hard drives, optical drives, all use the 12v rail, you don't want it to be weak..

 

[Amaroque]

I noticed you picked a "COOLMAX 400W CX-400B" for your PSU.

I would get a quaity name brand PSU. Why would you entrust all that hardware to a generic PSU?

There are a number of good quality brands. However, I've been pleased with Antec.

 

[ts3433]

18A of +12V power seems normal for that wattage of PSU (remember, the wattage number itself doesn't mean much, because standards for measurement vary wildly), and that should be sufficient. The brand might be a little iffy, though; consider Seasonic, Fortron, Antec, and Enermax. Seasonic's Super Silencer 400W has 22A on the 12V rail for around $85. The 350W variant has 19A on that same rail.

 

[flamingspinach]

So the current flow matters more than the total wattage? And how does this all work out? I'm no electronics major, but wattage is power, which is current times potential, or volt-amps... so shouldn't the 12 volt rail on a 400 watt PSU be at 33.3 amps (400/12)?

*confused*

And I only chose the CX-400B because it is the overall 4th rated PSU on NewEgg, by customer feedback, wattage aside... then again I bet people on this board know more than the general NewEgg customer base...

-fs

 

[ts3433]

Originally posted by: flamingspinach
So the current flow matters more than the total wattage? And how does this all work out? I'm no electronics major, but wattage is power, which is current times potential, or volt-amps... so shouldn't the 12 volt rail on a 400 watt PSU be at 33.3 amps (400/12)?

*confused*

No. In addition to 12V power, the PSU also must supply power at 3.3V and 5V. Wattage can matter too, but it's usually a good idea to check the rails because true rating can fall victim to marketing for generics a lot.

For some more guidance, check out reviews at SPCR (they really only review quiet PSUs, but that's all I'd really consider).

 

[flamingspinach]

Aha, so the "wattage rating" is really... OK crap, can't write sigma notation in plaintext, but... the sum of voltage times current for each of the rails? But doesn't that mean that a higher current rating on one rail means lower ratings on other rails?

I'll check out that site, hang on while I google it

-fs

 

[imported_brad]

PSU CALCULATOR

 

[flamingspinach]

With that calculator I got 311 watts... neat! Thanks for the link!

ts3433: I assume you mean http://www.silentpcreview.com/ ?

-fs

 

[ts3433]

That's the site I meant.

I wouldn't rely solely on any kind of PSU calculator, as they tend to be a bit inaccurate. Just get a quality supply like one they recommend at SPCR or that is confirmed to be very good by members around here and you'll be fine. This may also be of use.

 

[Childs]

I have the Seasonic Super Tornado 400W powering a A64 3200+, with 3 250GB 7200RPM 8MB drives, 1 120GB 7200RPM drive, 1 Pioneer 108, Audigy 2ZS, and a BFG 6800GT OC. I have no problems what so ever, so you should be fine. Personally, I would get something with more amps on 12v, but you should be alright.

 

[flamingspinach]

Wow! If you can run that much on 400W... whoo

Does more amperes on the 12V rail cause a compensatory reduction in amperes on the 5V or 3.3V rails?

 

[ts3433]

Yeah, there will be less than if the PSU was 400W for just 5V or 3.3V output, but you're generally not going to need more than 30A on each of those two rails.

 

[aatf510]

I personally would spend a little more on the speakers since you are buying a Audigy2 ZS.

 

[Regs]

A True 430 is the same one I have with just about the same type of system. It would be perfect.

 

[flamingspinach]

toattett: I really only got the Audigy2 ZS because of two things: soundfonts and EAX 4. I usually use headphones anyway, so speakers aren't a really big concern, I'll probably replace them later. The Codegen ones I selected were the best-rated by customer feedback in the <$40 bracket. I'm aiming for a total of around $1500.

Regs: Sorta on that note, when I originally started this thread, my listed PSU was the Coolmax Taurus CX-400B. I changed it thanks to ts3433's link to HardForum. This is why the price of the system is up to $1550, it was originally hovering at around $1510.

-fs

 

[imported_Phil]

I'm going to make a bigger post about this as soon as I have photos, but I was doing some PSU stress-testing at work on Thursday, with a Chieftec 360W PSU (dual 12v rails, 17A &amp; 15A). It was running a Prescott 3.4Ghz, 512Mb DDR-II, entry-level server board, two 120mm fans, three 80mm fans, and twelve hard disks in total.

That's five 10,000rpm SCSI disks in RAID-5, one on it's own, two Seagate 80Gb SATAs running the OS, and the rest were Maxtor 250Gb Maxline-II disks (7200rpm). Admittedly, the Maxtors weren't connected to the IDE bus and running, but the RAID-5 set was initialising, and the Seagates were running Windows, with Prime95 running on "highest power consumption" settings.

The voltages were being measured using a decent digital multimeter, and at bootup the 12v rail dropped to its lowest of 11.8v, but stabilised at 12v in Windows.

That's a total of twelve hard disks, all spinning up at the same time on power-on, and the PSU never complained, once.

More info as I write it up, but this goes to show that you don't need absurd 600W PSUs- quality is everything.

(Disclaimer: I know that running the Maxtors rather than just having them spinning would have created a higher load, but I was asked to find out at what point that PSU/board combo would stop POSTing.)

 

[aatf510]

Hey, you actually reply to me even though you don't need my idea. Thanks for you politeness!

 

[Amaroque]

Originally posted by: Regs
A True 430 is the same one I have with just about the same type of system. It would be perfect.

I have the True430 in a couple rigs. They are very strong for the rated output. I'd have to say the True430 is Antec's best value.

 

[flamingspinach]

Originally posted by: toattett
Hey, you actually reply to me even though you don't need my idea. Thanks for you politeness!

You're welcome ^^ Though I'm sure anyone else would have done the same.

-fs

Originally posted by: Amaroque

Originally posted by: Regs
A True 430 is the same one I have with just about the same type of system. It would be perfect.

I have the True430 in a couple rigs. They are very strong for the rated output. I'd have to say the True430 is Antec's best value.

Useful to know. Though it is a couple of deca$ pricier than the Coolmax, sounds like it will be worth it, judging by what everyone is saying.

-fs

 

[glugglug]

The 350W that came with my Antec case proved to be too weak for my 3500+ system, with too low voltage on the 12V rail. Granted I have it powering a RAID array, so all the drives means I have more load on the 12V line. Now using an OCZ Powerstream 520W, which lets you adjust the voltages manually.