Power Supply

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

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

"TboXx" wrote in message
m...
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

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

doughnut



"TboXx" wrote in message
m...
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

Actually U.S.

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

doughnut



"TboXx" wrote in message
m...
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

Try looking at:
alt.comp.hardware.homebuilt


On Fri, 13 Feb 2004 21:01:29 UTC, "TboXx"
wrote:

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


--
Fred Blau
(Change "s@" to "systematics@")

In article , "TboXx"
wrote:

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 = = 8.4A@12V
Athlon 3200+/FSB400/512KB = = 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 & +3.3150W
Turbocool 300 Dell 30A 12A 14A 0.3A 1A 2A +5 & +3.3150W
Turbocool 350ATX 32A 15A 28A 0.3A 0.8A 2A +5 & +3.3215W
Turbocool 425ATX 40A 20A 40A 0.3A 1A 2A +5 & +3.3300W
Turbocool 510ATX 40A 34A 30A 0.3A 2A 3A total510W

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

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.



"Jeff" wrote in message
news:R0bXb.489067$X%5.330841@pd7tw2no...
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

"TboXx" wrote in message
m...
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

This will sort your problems out.

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

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

"KJ" wrote in message
...
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.



"Jeff" wrote in message
news:R0bXb.489067$X%5.330841@pd7tw2no...
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

"TboXx" wrote in message
m...
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

"TboXx" wrote in message
m...
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.).