Power Supply

[TboXx]

I know this is a motherboard forum but im guessing you all would know if
your here anyway. Is there an easy way to tell what watt power supply i
should get? or any site you could direct me to,
Thanks

 

[Jeff]

Just get a good quality power supply at 300 Watts if you have a basic
system.
Your motherboard and Chip take most of the power... lets say 90 watts
together.
A hard drive takes maybe 10 watts at most... same with the CDROM drive. So
if the
power supply is good quality and can handle it's rated current under load...
should be no problem
with just 300 Watts... maybe... the Zalman 300 watt puppy... inexpensive
too.

Jeff

 

[Doughnut]

Are you in the uk? if so look here http://www.kustompcs.co.uk/

doughnut

 

[TboXx]

Actually U.S.

Are you in the uk? if so look here http://www.kustompcs.co.uk/

doughnut

 

[Fred Blau]

Try looking at:
alt.comp.hardware.homebuilt

I know this is a motherboard forum but im guessing you all would know if
your here anyway. Is there an easy way to tell what watt power supply i
should get? or any site you could direct me to,
Thanks

 

[Paul]

I know this is a motherboard forum but im guessing you all would know if
your here anyway. Is there an easy way to tell what watt power supply i
should get? or any site you could direct me to,
Thanks

A modern motherboard will have an ATX power connector and a 2x2 12V power
connector for the processor. So, you need an ATX power supply to power it.
At a minimum, those two connectors have to be connected to the motherboard,
to make it go. The 2x2 (i.e. four pin) connector is used exclusively by
the processor, and there is a conversion circuit on the motherboard, that
converts the +12V from the ATX power supply, into the 1.500V or so, that
a processor might need.

The ATX power supply has six outputs. The consumption from the -5V and
=12V outputs is so low, that there is no need to gauge the consumption.

The +5VSB output on the supply is used for "keep alive" power. That
power is used to save the contents of the DRAM chips, while the computer
sleeps. It powers the LAN chip, in case a wake up packet is sent to the
computer. It can be used to keep USB and PS/2 keyboards and mice powered,
so they can be used to wake a sleeping computer. If you download the
manual for the motherboard you plan on buying, there will be some
estimates in there as to how much power might be required. These aays,
many supplies have 1.5 or 2A for this function, and you can control some
of the load on this supply, by changing the USBPWRxx or PS2 PWR header
jumpers.

The +3.3V and +5V outputs on most supplies will be in the 20A or so
range. There is generally not enough information on power consumption
of the various parts of the computer, to say how much is enough. But
I can tell you by the process of deduction, that the consumption won't
be too high.

At one time, the processor derived its power, by converting the +5V output
to the lower voltage needed by the processor. With the increased power
consumption of processors, this function has been moved to +12V, and that
is why, if you try to reuse an old ATX power supply, chances are the
output on +12V will be insufficient for a new motherboard and processor.

To work out the numbers for +12V, seeing as it is critical, I use

Processor
P4 3.2Ghz/FSB800/512KB cache = [email protected] = 8.4A@12V
Athlon 3200+/FSB400/512KB = [email protected] = 6.4A@12V
including 80% conversion efficiency, the required current is
10.5A or 8A for a top end P4 or Athlon respectively.
Hard drive
2A during spinup of the disk, 0.5A while sitting in Windows desktop.
Allow 0.5A for a CD. If you don't have a lot of drives,
don't worry about spinup current, and concentrate on idle current.
Fans
Allow 1 amp for case and CPU fans.
Video card
Low end video cards use no +12V. An Nvidia FX5900 or an ATI9800
have a separate +12V cable, and as the video cards draw up to 70W
when gaming, a maximum of 6 amps would be required. Unless you
are buying one of these, a lesser number is more appropriate.
Total = 15A for a basic system, with some margin. If buying a
video card that requires extensive cooling, this number is more
like 20A.

Now, a reality check. The last computer I measured (2.6GHz/800 P4
865GE Northbridge) needed a total of 55W while idling in the Windows
desktop, and 120W while gaming (wall power). So, you can see that the
calculation above is quite pessimistic. That system didn't have a video
card, as it used the builtin graphics, so consumption could rise by
another 70W, if the system had a decent gaming video card in it.

Here are some sample products. The first table is for some
PCpowerandcooling.com products, considered the cadillac of power
supplies. For my purposes, the 350ATX meets the minimum +12V current
I would be after, so that is the smallest supply I would buy. You'll
notice that the bigger supplies mostly increase the capacity of the
rails you don't care about, so the 425ATX I would purchase to run
a FX5900 or ATI9800 has got a lot more +3.3V than I would ever need.

VOLTAGE ---> +5V +12V +3.3V -5V -12V +5VSB

Turbocool 300ATX PFC 30A 12A 14A 0.3A 1A 2A +5 & +3.3<150W
Turbocool 300 Dell 30A 12A 14A 0.3A 1A 2A +5 & +3.3<150W
Turbocool 350ATX 32A 15A 28A 0.3A 0.8A 2A +5 & +3.3<215W
Turbocool 425ATX 40A 20A 40A 0.3A 1A 2A +5 & +3.3<300W
Turbocool 510ATX 40A 34A 30A 0.3A 2A 3A total<510W

Here are the Antec Truepower series (antec-inc.com) - one step below
a cadillac.

VOLTAGE +5V +12V +3.3V -5V -12V +5VSB

TRUE330 30A 17A 28A 0.5A 1.0A 2.0A
TRUE380 35A 18A 28A 0.5A 1.0A 2.0A
TRUE430 36A 20A 28A 0.5A 1.0A 2.0A
TRUE480 38A 22A 30A 1.5A 1.0A 2.0A
TRUE550 40A 24A 32A 0.5A 1.0A 2.0A

Here, even the True330 is enough for a basic system, and the True430
is enough for a FX5900/ATI9800 gamer system.

Use a similar comparison with bargain supplies. Gauge them by output
currents and not total power.

HTH,
Paul

 

[KJ]

Basically correct. However, the more you add, the more power you need. Buy
a good quality (name brand) PSU with a little more power then you need now,
so you won't be in a jam if/when you upgrade or add-on down the road.

For example, I started with two 7,200 rpm HDDs, but now have five 7,200 rpm
HDDs, a Zip Drive (ATAPI), etc....all on my original Antec 330W PSU.

***** Also note the PSU's output on each voltage rail! Some claim high
total power, but skimp on the 12V rails. So you can see, even two 300W+
PSU's can provide different "quality" of power output. *****

You can sum up the total power for each device, by voltage rating, then use
the total power for each voltage rail as a MINIMUM guideline. I'd
personally take AT-LEAST 25% more then the total usage figures as the
minimum acceptable PSU rating for each voltage rail.

You don't want a sub-par PSU as you might experience some strange errors
that are extremely hard to track down or fix.

The simplest two things to be certain of:
1) Name brand quality unit
2) 300W MINIMUM for modern average machine, much more for server type of
setup and/or newer AGP graphics cards.

 

[Canus_Lupus]

This will sort your problems out.

http://www.jscustompcs.com/power_supply/

 

[KJ]

Paul beat-me-to-it with his excellent post later in this thread. Excellent,
and quite detailed, advice can be found in his reply.

 

[Darkfalz]

I know this is a motherboard forum but im guessing you all would know if
your here anyway. Is there an easy way to tell what watt power supply i
should get? or any site you could direct me to,
Thanks

Any good brand 300-400 watt should be fine. A good brand 250 watt will
perform better than a generic 400 watt, so obviously the most important
thing is to get a reputable brand (AOpen, Antec etc.).

 

[TboXx]

Thanks

 

[TboXx]

But what about that 800 watt supply that comes with that 10 dollar case.

 

[Creeping Stone]

I know this is a motherboard forum but im guessing you all would know if
your here anyway. Is there an easy way to tell what watt power supply i
should get? or any site you could direct me to,
Thanks

Any good brand 300-400 watt should be fine. A good brand 250 watt will
perform better than a generic 400 watt, so obviously the most important
thing is to get a reputable brand (AOpen, Antec etc.).

Is branding so important here? These are presumably quality assured
devices. I read Paul's Amp figures and my seemingly generic brand 350w PSU
seems to check out alright - its an 'eagle'

Seems that the current output details are rather more useful than the brand
names in this case.

 

[Darkfalz]

Is branding so important here? These are presumably quality assured

devices. I read Paul's Amp figures and my seemingly generic brand 350w PSU
seems to check out alright - its an 'eagle'

It's very important. Plain and simple, the cheapo generic power output
figures are LIES. I hooked a generic 400 Watt up to this same system, and
12v and Vcore levels dropped like panties under stress. The 250 Watt AOpen
that came with my case, only drops the slightest bit under stress.

 

[Jeff]

Just like guitar or stereo receiver amplifiers... some of them are rated at
peak wattage, other
are rated RMS. Some of the cheap power supplies to make themselves look
good... probably
rate their supplies according to peak output...not sustainable without
overheating or becoming
overloaded and suppliing inferior voltage levels and noise. Good power
supplies will have
overload and short protection and noise reduction circuitry and so on... in
addition to what
the cheap supplies offer. I think a Zalman 300W is a good starting point...
and it is rated RMS.
COnnect your PC to a UPS too... a cheap 500 Watt UPS keeps your system
healthy too.

Jeff

 

[Doug Ramage]

It's very important. Plain and simple, the cheapo generic power output
figures are LIES. I hooked a generic 400 Watt up to this same system, and
12v and Vcore levels dropped like panties under stress. The 250 Watt AOpen
that came with my case, only drops the slightest bit under stress.

Some general info here too:

http://www.firingsquad.com/guides/power_supply/

 

[Creeping Stone]

Is branding so important here? These are presumably quality assured
devices. I read Paul's Amp figures and my seemingly generic brand 350w PSU
seems to check out alright - its an 'eagle'

It's very important. Plain and simple, the cheapo generic power output
figures are LIES.

I suppose that could be true, but wouldnt expect it to be the norm, with
electrical product regulation the way it is, - in the UK at least.
It makes sense for all economically developed countries to heavily check
electrical equipment sold - or too much expensive fires and accidents could
result.

I hooked a generic 400 Watt up to this same system, and
12v and Vcore levels dropped like panties under stress. The 250 Watt AOpen
that came with my case, only drops the slightest bit under stress.

No info here though^ No details of the specified output per rails, and from
one unelaborated report -I am to assume that all Brands will excell beyond
their adverts and all blank boxed units are dishonest ripoffs

Being a no logo type of guy myself, I meekly suggest you are just
perpetuating the usual big logo consumer conditioning which many seem to
hold dear.

So you get corsair, lan-li, antec, plextor, raptor....
good for you,
I dont rekon its worth the extra expense -especialy when you can check
specs yourself, and as I said, its rather illegal in my country at least to
lie about electrical products technical capabilities.

-I think .

 

[Stephan Grossklass]

Is branding so important here? These are presumably quality assured
devices. I read Paul's Amp figures and my seemingly generic brand 350w PSU
seems to check out alright - its an 'eagle'

It's very important. Plain and simple, the cheapo generic power output
figures are LIES.

I suppose that could be true, but wouldnt expect it to be the norm, with
electrical product regulation the way it is, - in the UK at least.
It makes sense for all economically developed countries to heavily check
electrical equipment sold - or too much expensive fires and accidents could
result.

But does that say anything about the output performance or build quality
of a PSU? No, rather not. In terms of power supplies, you usually get
what you pay for. A decent 300 W Fortron (aka FSP Group, Sparkle, AOpen;
Zalman also uses those) PSU costs 40...50 EUR here, and not without a
reason. Of course you can buy "550 watt" units for 30 EUR, but it's not
very likely that these can actually live up to their claimed specs. (A
300W Fortron, on the other hand, was able to run a system with an o/c'd
P4 3.06, Padeon 9700 Pro, and a bunch of hard drives perfectly well
according to a review.)

I used to have a "300W" DEER PSU, and those are most probably some of
the worst low-quality crap ever produced (around 2000/2001 I think).
Very lightweight, thin cables, and even the specs were worse than on a
good 250W PSU.
In terms of contemporary PSUs, COBA is not much better than that,
Levicom is so-so, Enermax quite OK but usually hyped, Tagans have earned
their reputation among PC silencers and should also be quite good
electrically, Antec PSUs are supposed to be among the best. Fortrons are
also very good, maybe not quite as high-tech as some others but good
value. (OEMs frequently use them.)

This box here is powered by a rather popular OEM choice of a few years
back, a 110 watt Astec. One guy I know installed a second 60 mm fan
(blowing inwards) in one and ran a full-blown Athlon XP 1600+ equipped
system (with K7S5A, 1 gig of DDR SDRAM, GF4MX440, hard drive, DVD and
whatnot) off it - no problem. (My system here is much less power hungry
than that, roughly comparable to what the PSU originally shipped with.)

Being a no logo type of guy myself, I meekly suggest you are just
perpetuating the usual big logo consumer conditioning which many seem to
hold dear.

Nah, you merely don't know what you're talking about. There are a few
things where buying quality pays off, among them critical parts like
power supplies. Keyboards are another example (you mostly get crap
that's terrible to type on these days; I have yet to see a Cherry G80 in
a shop). Of course it's necessary to distinguish between mere hype and
real quality. (Logitech keyboards are more the first, while their mice
are more the latter.)

So you get corsair, lan-li, antec, plextor, raptor....

A very interesting mixed list. The expensive "low-latency" RAM modules
sold by Corsair and other companies indeed do not excel in terms of
price/performance (I'd prefer solid Infineon or Samsung stuff), but
what's the WD Raptor doing there? The 74 gig Raptor is by far the
fastest hard drive with a "consumer level" interface you can buy,
period. You may want to consult the storagereview.com performance
database. When placed against the second fastest SATA drive there, the
250 gig Hitachi 7K250 (no slouch in itself), it's 27% to 57% faster.
That's 15k SCSI territory - minus quite a bit of the heat and noise.
(Unfortunately, /me is perpetually broke.)

Stephan

 

[Creeping Stone]

Is branding so important here? These are presumably quality assured
devices. I read Paul's Amp figures and my seemingly generic brand 350w PSU
seems to check out alright - its an 'eagle'

It's very important. Plain and simple, the cheapo generic power output
figures are LIES.

I suppose that could be true, but wouldnt expect it to be the norm, with
electrical product regulation the way it is, - in the UK at least.
It makes sense for all economically developed countries to heavily check
electrical equipment sold - or too much expensive fires and accidents could
result.

But does that say anything about the output performance or build quality
of a PSU?

The rail ratings specify the output performance, their veracity and the PSU
build quality should be ratified by the relevant authorities responsible
for insuring and prosecuting against Sky scrapers and districts going up in
flames.

No, rather not. In terms of power supplies, you usually get
what you pay for.

Unless your paying for brand names, PR, fake reviews etc..
The heavyweight post in this thread said to pay attention to the
line ratings - not particularly the brand.

A decent 300 W Fortron (aka FSP Group, Sparkle, AOpen;
Zalman also uses those) PSU costs 40...50 EUR here, and not without a
reason. Of course you can buy "550 watt" units for 30 EUR, but it's not
very likely that these can actually live up to their claimed specs. (A
300W Fortron, on the other hand, was able to run a system with an o/c'd
P4 3.06, Padeon 9700 Pro, and a bunch of hard drives perfectly well
according to a review.)

I used to have a "300W" DEER PSU, and those are most probably some of
the worst low-quality crap ever produced (around 2000/2001 I think).
Very lightweight, thin cables, and even the specs were worse than on a
good 250W PSU.
In terms of contemporary PSUs, COBA is not much better than that,
Levicom is so-so, Enermax quite OK but usually hyped, Tagans have earned
their reputation among PC silencers and should also be quite good
electrically, Antec PSUs are supposed to be among the best. Fortrons are
also very good, maybe not quite as high-tech as some others but good
value. (OEMs frequently use them.)

This box here is powered by a rather popular OEM choice of a few years
back, a 110 watt Astec. One guy I know installed a second 60 mm fan
(blowing inwards) in one and ran a full-blown Athlon XP 1600+ equipped
system (with K7S5A, 1 gig of DDR SDRAM, GF4MX440, hard drive, DVD and
whatnot) off it - no problem. (My system here is much less power hungry
than that, roughly comparable to what the PSU originally shipped with.)


Nah, you merely don't know what you're talking about. There are a few
things where buying quality pays off, among them critical parts like
power supplies.

I try to pay attention to the honest breadth of my understanding and relax
sometimes to..relax, and test extensions. I dont think Ive spoke out of
turn here though, Im havent suggested saving money on power supplies, I can
see the advantage in being particularly selective with them.

I rekon if you pay x for a generic power supply it will on average be a
superior supply than if you spend the same amount on a branded one (!)
-Know how that economy works ?

Keyboards are another example (you mostly get crap
that's terrible to type on these days; I have yet to see a Cherry G80 in
a shop). Of course it's necessary to distinguish between mere hype and
real quality. (Logitech keyboards are more the first, while their mice
are more the latter.)


A very interesting mixed list. The expensive "low-latency" RAM modules
sold by Corsair and other companies indeed do not excel in terms of
price/performance (I'd prefer solid Infineon or Samsung stuff), but
what's the WD Raptor doing there?

This was just a list of top quality brands to set the scene, Im not dumping
on them, Im dumping on the idea that they are what everyone should aspire
to.
You can run to the shops in an Audi or tour the highlands in a old Skoda.

(Unfortunately, /me is perpetually broke.)

Its a righteous way to be :]

 

[Philip Callan]

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Creeping Stone wrote:

|
| So you get corsair, lan-li, antec, plextor, raptor....
| good for you,
| I dont rekon its worth the extra expense -especialy when you can check
| specs yourself, and as I said, its rather illegal in my country at
least to
| lie about electrical products technical capabilities.
|
| -I think .

Like this page:

http://www.antec-inc.com/pdf/article/info_DIYArticle1.html

Which will explain a lot about generic vs real brand PSU's, and explain
load testing and how even a good 350W can outpower one of the no-name
500W POS's

Philip
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