Article: Powersupplies!
Hi dude's and dudettes(revision 1.0)

Let's talk about power supplies, as this is getting to be a really big problem.

Start with this:

Link to AMD approved powersupplies

Note that this guide was written BEFORE the release of Barton core based processors!!!! Thus the need for HIGHER amperage output of the 12V rail from a power supply. Minimum should be 18 or 20A to ensure proper current feed for your power hungry devices.

Ok, here we start!:

Many people think that the wattage on a powersupply is the same on every powersupply. Well this is NOT the case...

Most cheap powersupplies have a label on them that just fits the needs of the company that sells them. Power supplies have peak and continuous power and most cheap brand power supplies (PSU for short) print Peak power ratings if they print anything at all...

The more decent PSU labels show Continuous power ratings.

In short, Cheaper PSU's rated for 300W does NOT mean that it is usable 300W.

As most systems today need a lot of power, you best try another first if you have problems, especialy if you think or determine that you have a cheap one.

In my system I use a 250W PSU or AOpen (AMD approved upto AMD XP1800+) and it can deliver about 16A at 3.3V and 25A at 5.5V, combined power about 150W for 3.3 + 5V.
Well you might start to laugh about this little baby, but it does deliver way more then most 300W PSU (sometimes even rated higher) cheap ones.
My favorite PSU is Powerman 300W it can deliver 28A 3.3V, 30A 5V and the combined power is 200W for 3.3+5V (model number FSP300-60BTV(PF)) and it's big enough to handle the most heavy systems today.
But they are talking continue power, not peak power.
A good example of this are speakers, they are sold today with powers upto 1000Watts and more, when the can't even deliver 1/10th of it (or less).

(Note from editor: He makes no reference to the 12v rail in this paragraph which has become a bigger issue recently with the release of the newer processors on the market. The mfg's of PSU's have released supplies on the market prior to really knowing what the power consumption would be of the new processors and thus some fall way short of being capable in a good rig. This isn't even to mention that we've now thrown the Graphical Processing Unit (GPU) into the 12V fray. So now you have to plug in your video card directly to the PSU and thus you have a higher current draw again so upping that 12v current rating has become a reality. Bonz)

The problems with power supplies that don't provide enough amperage can range from:

Not starting.
Crashes in the BIOS.
Bought a new videocard and it doesn't run anymore.
High pitch noises.
Crashing randomly.
OS not installing.
Crashing when playing games.
CPU FSB won't run at 133MHz.
Drivers not installing.

You name it...the system is trying to feed power to all of the components at once and it just doesn't have it to give so it goes into a shutdown mode to keep it from catching on fire. It's a failsafe that's built into any GOOD PSU manufacturers' product.

Alway's make sure you have enough juice to power your system. An AMD system needs enough power, 220W combined and 216W for the 12V rail, and most older 300W and prior aren't capable of reaching these values. So alway's make sure you have an AMD approved PSU AND make sure it's approved for your CPU type or above....

You can calculate this on your own using Power=Voltage X Current.

You can also use this as a basis for determining what PSU specs to use and it's a bit more fun too! This way is also a bit misleading in that a lot of motherboards are using more integrated components causing them to draw higher power than is listed on this page. I would say 25W is way lower than should be for todays motherboards. So I would add in those components anyway to get a more realistic idea of the power draw. A good example would be to add in the Soundblaster in place of onboard sound which they don't list but it still draws power from the MB. And yes in some cases you'll come up with a way higher number sometimes than you should.


For modern CPU's (XP-1800TBred and up) and motherboards the following should be checked:

3.3V 24A or above
5V 30A or above
12V 18A or above

Combined 3.3+5V somewhere around 200W
Test another PSU with a friend or your dealer, see what happens.
Cheap 350W PSU's don't cope well with modern systems, this doesn't mean they fail in all situations, just that they might fail.
The problem with PSU's is that it might look like the problem and not be but the only way to find that out is by replacing it and testing. This can be true in unison with a memory issue. Example: You replace the PSU and the memory is still causing the problem. You change back to the old PSU insert new memory and still fail. Two separate issues but the same result overall for both failures. This is a real hairpuller situation, but it does happen.

Another update!
Many new motherboards sound an alarm when they're underpowered. Sometimes it sounds like a siren.

Another note to think about is that Intel based rigs usually don't require the same high output as AMD rigs but sometimes they do so keep that in mind for the Intel users out there.

Written by Bas
Edited by Bonz 2-16-2004

So now you know what to look for when asked, by a user in the forum, what your specs are for your PSU.

Added by Wonkanoby

Another good site with tons of info on many issues and is presented well:

Short Media

Input provided by Rick_G


it means that
+3.3V 28A
+5V 25A
+12V 12A
+5V N +3,3V TOTAL O/P 188W

is not enough for AthlonXP 2000+ ?
Is this a reason that my PC do no start and I hear a sound like fire horn ?



The importance of clean power is so overlooked today. 90% of all the issues I encounter with people are fixed with a good power supply and a UPS. People are willing to spend $400+ on a videocard but don't want to spend more than $20-$40 on a PSU. Then they wonder why there system is so unstable. You get what you pay for!!! This is definently not the area to skimp on. Clean power is good power.


hi there, built a system recently, everything works fine apart from........MY SYSTEM WON'T SHUT DOWN!!!

say i click on the start button in windows(XP), then click on "shut down", then it says window is saving users settings and shutting down, when the screen goes blank and black normally it means all set and lights out, well in my case the system cuts off power(which is good)for 2 seconds(which is not good) then restart again!! i tried to use the power on/off button in DOS but still wont make any difference, power seems to be cut for 2 seconds and then restarts again.

i am using a KT4V-L mobo (with standard BIOS, hasnt been updated yet) with the following spec:
AMD XP2000
ATI Radeon 9000pro 128mb DDR
a unbranded 4ch sound card(disabled as using on/board sound)
a intel pci v.92 56k modem
80gig 7200rpm ata100 HD
unbranded DVD rom
unbranded 52x32x52 CDR
1.44 FDD
can anyone help please???



New member
Jul 7, 2002
try disabling wake on lan and any other wake on you find in the bios


I'm having some booting problems (sometimes, especially when exiting CMOS I get beeps and d-bracket hangs on "Memory Detection Test"). Using lower FSB and disconnecting the 12V connector helped a little.

I'm also getting some noise from the optical output and I think it could be caused by too weak signal. (Removing modem and replacing graphics card helped on this, but not completely)

Do you think I need a more powerful PSU for my system? My current specs are:

+5V - 35A
+12V - 18A
+3.3V - 28A
-5V - 0.5A
-12V - 1.0A
+5V SB - 2.0A

+5V, +12V and +3.3V max load 360W


New member
Jul 7, 2002
whats the combined 3.3 and 5 v over 200 watts?

make and model might mean some thing as well


It's Antec TruePower (True 380 SP) supplied with the Sonata case. It has "dedicated output circuitry for each voltage output" so the combined power of 3.3V and 5V shouldn't be a problem.


New member
Mar 11, 2003
I just checked my V2.2 Bios for my GNB MAX-FISR, and under the section on PSU voltages, what I found is something like:
+ 5.02V

How does one ascertain the voltage specs for the MB? I presume the slightly high voltages on the negative rails are not a big deal, but at some point these relatively high voltages could be an issue. And I'd like to know at what point I should be concerned. Next time I open the box, I will tweak the voltages more toward their -5.00 and -12.00 targets. I presume I can easily find the potentiometer screw for this? Any comments? Thx.


P4, 2.53 GHz, 533 FSB.
4xKingston 512MB DDR-266.
MSI GeForce4 TI4200 AGP8X 128MB
2x120GB Seagate BArracuda SATA drives, 7200 RPM.
160GB Western Digital Caviar, 8MB Cache
WinXP-Home, SP1.


New member
Jul 7, 2002
do not mess around inside a psu ,and they are allowed plus /minus 5 percent,and 10 percent as far as 12v goes

however a good psu will be within 3 percent

in reallity bar latest antec there is nothing you can adjust,and quite often the monitoring not accurate any way

my antecs allways read under ,but a volt meter confirms its spot on



Is the Antec TruePower (True 380 SP) a good power supply because I just got one of this.

Thank you for your attention.


New member
Jul 7, 2002
pretty stupid question without the signature to show what its supposed to power

older low end set up fine

newer board and cpu and vga card forget it with only 12a at 12v


something puzzles me.
i suppose most psu-makers know for what purpose their psu will be used for and
i also suppose they know what power the differant pc-components needs.

why does the 3,3/5/12v a-numbers differ from a brand to another - do they see things differantly.
for example is a high 12v number more important then the 5v and so on.

some examples to clarify the question;
Antec 480w - spec. 3,3v=30a / 5v=38a / 12v= 22a
Enermax 431w - spec. 3,3v=38a / 5v=44a / 12v=20a
PCPower 510w - spec. 3,3v=30a / 5v=40a / 12v= 34a

i am not really talking about good or bad psu here, more trying to find out if there any reason to look for "special good"combination of watts and 3,3+5.12v and if its possible to speculate which v- will be more used/demading with the upcoming pc components next year.



New member
Jul 7, 2002
older amd boards feed the cpu of the 5v and 3.3v rail

newer are all coming of the 12v

older gf 4600 also feed of 3.3 and 5 v

newer cards all feed of the 12v

so now the 12v rails the most important and i think thats likley to stay

thats an older enermax spec you quoted,the new ones

35a 35a and 33a and reflects what i just said

im sure if antec redesign there 12v amps will shoot up as well