How many Watt PSU do I need for this setup?

O

Operaghost

[H]ard|Gawd
Joined
Jun 4, 2004
Messages
1,315
Abit IC7
P4 2.8c or 3.0c
1 SATA HDD
1 Optical Drive
X800 Pro
Vdimm at 2.8V
5 x 80mm Fan
4 x 12" CCFL's

Would a Fortron 400w be enough juice or should I go 530 or 550?
Also is PFC worth having?
 
A Fortron 400 W would definitely be enough for that setup, but like with all upgrades, give yourself some breathing room. Get like a 450 W model so you can be safe if you start doing a lot of overclocking or add more hard drives.
 
watts isnt the measure that is important.
the question should be:
What PSU will have the proper amp distribution to the assorted rails
to match my components?


well basically you add up the rails with this calculator
http://takaman.jp/D/index.html?english
and compare it to the specs listed on the PSU
then you build in a safety margin of from 1\2 to 1\3rd
by deducting 1\2 to 1\3 the value of the PSU's rated amps and see if it still fits
it actually varies with the distribution ratios your likely to need more +12V than +3.3V or +5V
(CPUs now being powered by the +12V primarily)
possibly more if it a long term infrastructure investment and there is growth built in
of if the veracity of the manufacturer is in question (generics tend to lie like dogs)
most 250 or 300 watt PSUs will actually run most configs, but stability has become an increasing concern with the tighter tolerances onboard (FSB)

There is a decrease in total capacity with the rise in temperature , which reduces your amps, the rated amp values where taken at 25C
while your likely operating temperature will be 40C (especially if the PSU is in the top of the case exhausting the CPU HSF) and that is roughly a 30% decrease

That is offset by the additive nature of the calculator, employing all tha maximum draw figures for the assorted components, something that will never occur

However it gets even more complicated if you have alot of drives and fans, those are typically given a "run time" draw value in a calculator, there "spinup" draw can be 4 to 5 times as much and they greatly contribute to transient response overshoot and undershoot in some supplies at startup if there isnt enough +12V

The way you torture a power supply is to give it a fluctuating AC feed to deal with (from surge to brownout), at the same time you ask it to deal with a really dynamic internal load change (like spinning up alot of drives) while still keeping the rails stable enough for the onboard voltage regulation components of unknown quality :p

Failure anywhere along the chain from too big a spike at the source to too long or high an overshoot or undershoot to the mobo, with too much ripple or noise for the onboard regulator to deal with and RAM or other components can go bye bye, ideally the power supply will trip off and protect your components, the operable range it has is largely what the difference in one PSU to another is about. And when it comes to a comparision of a flyweight generic, the whole protection scheme of shutting down in time really comes into question. And of course how stable the rails can be maintained, how low the AC Ripple and noise.

so if you elect to get a supply in the near future you have to ask yourself
if its going to be a true infrastructure investment
in the past that was typically true, now it a little tougher with more power hungry devices
PCI Express, video cards ect.

They recently added 4 more pins to the main connector from 20 to 24, and an additional 4 pin +12V auxillary power connector, (ATX12V 2.0) and the spec keeps jumping the total amps on the +12V rail (ATX12V 2.0 & 2.2), actually there are now two +12V rails and Ive seen power supplies that have Quad rails

ATX12V v1.1 (ATX 2.03 standard) is a 20 pin PSU with a 4 pin +12V connector
but if your considering a long term investment the most important thing for you to determine is the number of pins the mobo connector has, and get a ATX12V v2.2 compliant power supply (unless you need an SSI Compliant EPS12V), and if you have a 20 pin connector see if it can be attached directly with a 24 pin PSU or if an adapter is needed (cap clearence)

as far as what your rails are reading in a monitoring program, for starters,
you cant observe that during startup with software or the BIOS

here is a Codgen300X1 under a dyanmic load
Codegen300X1.jpg

from > http://terasan.okiraku-pc.net/dengen/tester/index.html
and > http://terasan.okiraku-pc.net/dengen/tester2/index.html
(but hosted independently)
note the instabiliy at spinup (an extreme example, but thats common if you review the links)

compared to a PC Power & Cooling 450ATX
PC Power450atxs.jpg

same source

so Ideally youd like to use a Digital Multimeter to read your rails directly, watch the spinup,
and then if you can find a realtively stable voltage state use it to calibrate the voltage your reading on the DMM to the software (easy to do in MBM)

a bit more cut and paste
-----------------------------------------------------------------------------------------------

Continuous Power vs. Peak Power at Spin-Up
12V power profile (current vs. time) of an IDE/ATA hard disk at startup. You can see that the peak power draw is over quadruple
the steady-state operating requirement. The graph appears "noisy"
due to frequent oscillations in current requirements
Click to expand...

Peak vs. Continuous Power
Despite this extra capacity, it is still a good idea to not load up your system to the very limit of your power supply's stated power capacity. It is also wise, if possible to employ features that delay the startup of some disk drive motors when the PC is first turned on, so the +12 voltage is not overloaded by everything drawing maximum current at the same time.
Click to expand...

"the majority of damaged RAM returned to memory manufacturers is destoryed by fluctuations in the voltage."
http://www.anandtech.com/showdoc.html?i=1774&p=8

Winbond Launches New Bus Termination Regulator April 4th 2003

"Winbond Electronics Corporation, a leading supplier of semiconductor solutions, today launched the W83310S, a new DDR SDRAM bus termination regulator. The solution, new to Winbond's ACPI product family, is aimed at desktop PC and embedded system applications with DDR SDRAM requirements.

Computer systems architectures continue to evolve and are becoming more complex; CPU and memory speeds continue to increase ever more rapidly with every technology turn. More and more high current/low voltage power sources are required for PC systems. This is particularly true for high-speed components such as CPU, memory, and system chipsets. The performance of these components is highly dependent upon stable power. Therefore, motherboard designers require accurate, stable, low-ripple and robust power solutions for these components.

Many system designs use discrete components to implement bus termination functions. This approach creates several problems including poorer quality load regulation; higher voltage-ripple, increased usage of board space and inconsistent designs when different discrete components are used."


http://www.anandtech.com/showdoc.html?i=1774&p=8
"the majority of damaged RAM returned to memory manufacturers is destroyed by fluctuations in the voltage."

the transient response is the critical internal measure, unfortunately its not a metric that is commonly supplied with the PSU specs
(this seems to be slowly changing, as some manufacturers are supplying the transient response now)

Transient Response: As shown in the diagram here, a switching power supply uses a closed feedback loop to allow measurements of the output of the supply to control the way the supply is operating. This is analogous to how a thermometer and thermostat work together to control the temperature of a house. As mentioned in the description of load regulation above, the output voltage of a signal varies as the load on it varies. In particular, when the load is drastically changed--either increased or decreased a great deal, suddenly--the voltage level may shift drastically. Such a sudden change is called a transient. If one of the voltages is under heavy load from several demanding components and suddenly all but one stops drawing current, the voltage to the remaining current may temporarily surge. This is called a voltage overshoot.

Transient response measures how quickly and effectively the power supply can adjust to these sudden changes. Here's an actual transient response specification that we can work together to decode: "+5V,+12V outputs return to within 5% in less than 1ms for 20% load change." What this means is the following: "for either the +5 V or +12 V outputs, if the output is at a certain level (call it V1) and the current load on that signal either increases or decreases by up to 20%, the voltage on that output will return to a value within 5% of V1 within 1 millisecond". Obviously, faster responses closer to the original voltage are best."
 
Man that's complicated...power is hard :D

Most people don't want to have to go through figuring out max's and min's that will be drawn by their devices, though some of us will. I'd say a majority just want a quality power supply that will run everything they have and do it with some degree of stability. For that reason, this guy doesn't really need to do a lot of calculations. If he gets that 400 watt Fortron model I'm sure it will power what he has. With a trustworthy company like Frotron, you can expect that as the wattage rating goes up, the rails go up in some corresponding fashion.

Now, everything you posted is right on, I'm not saying all that is useless, but it is more trouble than is needed for the average bear.
 
LOL, but the primary function of the forum (and my job) is education :p
yes that power supply will do the job in all likelyhood

and when he comes back with four other models that are cheaper
how should he assess the difference?

understanding the tradeoffs and the risks is important, specially on a budget
determining the quality of the power supply, guessing the quality of the Voltage Regulation onboard and eliminating power fluctuations from the outlet, are things that he should really try to do.

Beats the hell out of buying a whole new computer, because he was using a cheap surge protector with an MOV that burned out, frying the supply beacuse it had a faulty fuse and power regulation or worse taxing it so much that it was unable to supply a voltage within spec that inturn the mobo passed on to the FSB frying RAM or the CPU \ chipset.

education is a good idea in Power Supplies
its the component with the highest probability of killing other components ;)

ignorance is bliss
until reality knocks on your door with a big helping of pain :eek:

Im now pretty confidant that Ive killed 2 mobos through poor power
the thing that threw me, was that I had another mobo (and still do)
that had a more robust voltage regulation and is still working flawlessly
with the power that killed the other 2
 
That graph of the PCP&C is dead on 12.00v - out of the other smooth graphs, very few were dead on like that.

- The Enermax 651W was jumpy and at 12.5V
- The windy dropped to 11.9v
- The Ablecom was close
- The Antec was smooth; at 11.9v
- Zippy had a ripple at 12.25v

The others were pretty consistently inconsistent.


Pretty impressive product.. Thanks for the research
 
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