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I am building an AMD64 4000+ and NVIDIA, 6800GT which I know requires
external power source form PSU, do you think a 350watt PSU could withstand
that CPU, GPU, HDD and CD RW. I have heard a good one should be able to, but
then I have also heard going for a 500 watt would be a better option

any help be great


Re: 350Watt

500 Watts?  Not for that setup!

Read the following post I found:
"I have an Athlon 64 3400+, 1024mb ram, a DVD burner, 9800 pro, a TV tuner
and a PCI ide controller with a total of nine hard drives, 8 ide and 1 sata.
PSU is a 350W Antec Silent Blue
It is beautiful"

So, as long as you have a half decent PS, you shouldn't have any problems.
All problems have a simple solution!  The more complex the solution, the
more ludicrous the analogy!

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Re: 350Watt

chris wrote:
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Possible, but you wouldn't want to run the system under load for extended
periods of time. First of all, there is no Antec Silent Blue power supply.
I'll assume he's running a SmartBlue 350, which seems to be the closest fit.
The ratings on this PSU are:
+12V : 16A
+5V : 35A
+3.3V : 28A
with the cross-cload restrictions of 5V + 3.3V < 330W and 5V + 3.3V + 12V <

A modern 7200 RPM HDD drive consumes somewhere between 7W and 10W when idle,
almost exclusively from the 12V line. So 9 HDDs would use at least 5.5A from
the 12V line. A 3400+ typically eats 3A+ when idle, possibly more if it's a
low end motherboard (less efficient regulators). When idling, a 9800Pro uses
3.6A from the 5V line, 0.3A on the 12V line, and 2.9A on the 3.3V line. So
our idle current requirements are:
+12V: 12.1A
+5V: 3.6A
+3.3V: 2.9A
5V+3.3V : 27.6W
12V+5V+3.3V: 172.8W

Under load, a 9800 Pro consumes ~5.4A from the 5V, 0.6A from the 12V, and
4.4A from the 3.3V. A 3400+ will require at least 6A from the 12V line,
probably actually 7 or more depending again on motherboard quality and core
revision. An active HDD typically consumes 1A from the 12V line. So, if we
have the CPU and GPU under stress (eg: gaming) the current requirements go
up to:
+12V: 16.4A
+5V: 5.4A
+3.3V: 4.4A
5V+3.3V : 36.6W
12V+5V+3.3V: 238.4W

So we're already over the rated value for the 12V line. And this is without
the RAM, PCI cards, or chipset requirements taken into account. Throw in an
active HDD or two (a level load from a RAID0 array, say) and we're starting
to get significantly over the  rated power for the PSU, even from an
under-predicting calculation. Sure, it might work for a while, but I for one
would not be betting on the life expectency of the PSU, or even system
stability under load.

Another real killer on that setup would be the HDD spin-up. I know that PATA
does not support sequential spin-up, and I'm pretty sure SATA doesn't
either. The spin-up for a typical 7200RPM drive is somewhere around 3A (the
older the drive the more it uses). So 9 drives spinning up would require at
least 27A from the 12V line (324W) . I'm guessing that if you stuck a
multimeter onto the power supply you'd see a huge current sag during

For the OP's system, a good quality 350W would probably just scrape in. I'd
feel much more comfortable with a (good quality) 400W or 450W. 500W and
above is probably overkill unless you're going to be going for a high
overclock on the card and CPU (mainly increasing the voltages will be what
gets it).

And this is coming from someone who used to talk down big PSUs ... :)


Michael Brown
www.emboss.co.nz : OOS/RSI software and more :)
Add michael@ to emboss.co.nz ---+--- My inbox is always open

Re: 350Watt

My Antec SL350 works great in my system shown below. I built this system
about 8 weeks ago.

            AMD 3700+ San Diego @ 2.6 Ghz/Retail HSF
            MSI Neo2 Platinum/Bios 1.8
            OS: Win XP Pro/SP2
            Antec SmartPower 350W +3.3V/28A   +5V/35A  +12V/21A
            BFG 6800GT OC 370/1000
            1 Gig OCZ PC3500 2.5-3-3-7-2T Dual Channel
            Maxtor 250 Gig ATA 133/Primary IDE Master
            WDC 80 Gig ATA 100/Primary IDE Slave
            Seagate 160 Gig SATA on SATA3
            Plextor DVDR PX-708A Sec. IDE Master
            Liteon JLMS XJ-HD166S Sec. IDE Slave
            Turtle Beach Santa Cruz Sound Card

Re: 350Watt

I have an AMD643400+ 512 DDR400 2 cd drives, 1 HDD, geforce 4 and I had a
550watt until fan broke, now im on a 350wat and it works but my system
doesn't run as it did, not sure if that's PSU related, ill try it with the
350 watt, see how it runs, do a few burn-ins if needed ill up to 400-500

Tanks for the help

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Re: 350Watt

It will suffice for the time,but keep in mind it runs at max power with your
So if this psu brakes down on you ,you know why that is then.
Just be sure you get a quality psu to replace it,i got a realpower from
coolermaster,and it's guaranteed to deliver 450w constant.
So yes,if my system needs more the board will shut down or something like
that,but i won't burn my psu to ashes when this happens.

In real life you have to use all of your components at once to drive the
maximum power required through your psu,and normally the greates boost is at
So that's why ppl run their pc with underpowered quality psu's without
But remember,the cheaper psu's,even the 600w or higher ones,are not as
reliable as the lower end quality psu's.
Not in the long term anyways...

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Re: 350Watt

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Fix the fan. Shouldn't be that hard to replace. Find a fan that fits and
strip the wires because usually the PS fan connector is a two pin connector
or better yet if it's PS made by a major MFG see if they will sell you one.

PS failures are rather insidious, mysterious crashes, BSOD's and the like.
Of course when you reboot everything seems fine.

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