# Getting the right Power Supply

Discussion in 'QnA (read only)' started by gxsaurav, Sep 3, 2005.

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1. ### gxsauravGuest

These days, when people buy a powerful new computer system, weather based on athlon64 or Intel Pentium 4, or Celeron D or Sempron, weather they buy a 6600GT or 6800GT, they forget about the most important & vital component of the system, The SMPS.

SMPS stand for Switch Mode Power Supply, one myth people have that with a high power SMPS, in wattage, they will get high electricity bill, but itâ€™s wrong, even if u have a 800W SMPS, if u use only 300W, then the rest of the 500W is simply working idle & wonâ€™t add up to the electricity bill.

Usually people go with the SMPS bundled with the cabinets they choose, cos the price is included in it, now in many cases, this bundled SMPS is enough for the tasks, but in few cases itâ€™s not, because of which is advised to go for a discreet Power supply. Also with the ATX 2.03 specification, Intel & AMD require a 24-pin power supply, & PCI-E based cards also needs extra power

To calculate how much power supply U need, I strongly recommend that you visit here,which can give u a pretty solid rough measurement of your power needs, for your components

Now, U know your power needs, itâ€™s time to calculate how much actual wattage your SMPS will provide, the best way to do is to check it by an electrician, but u can calculate it on your own too

All the SMPS, weather bundled or not, come with a power supply measurement label applied to them, basically itâ€™s like this

+12v = xx A
+3.3v = xx A
+5v = xx A etc

We use simply the equation

Power (W) = Volt X Ampere

Now calculate, it, & U will get the exact measurement about how much wattage your SMPS can actually provide. But, since there is always some loss due to heat, decrees 5% of the total wattage of the SMPS from the total wattage

Suppose U have a 400W power supply, which gives about 350W power when calculated by the above formula, and then simply subtract 18W from it, as heat loss. This new value is the actual power of your SMPS

Right now, in India, exotic power supply brands like Antec or Enemax are hard to find & if found they are costly, a lot costly. U can go for a few good alternatives, like VIP, Powersafe, and a fairly new-comer here these days Colorsit, I gave a Colorsit SMPS to a friend a few days, ago , the Model number is M-330U, which as calculated by the label gives 425W power, so itâ€™s about 410W approx. which is shockingly good.

They also have a Silent Power 12 CM version which has a 12 cm, fan just above the CPU, blowing air outside, & indeed it is silent, the ceiling fan makes more noise. The other options are Standard Model & a Dual fan model, U can check them here

For a thumb rule, I m providing an estimate calculated power for system having

Celeron D & Sempron = 260W
Athlon64 = 340W
Pentium 4 LGA775 = 350W

Keep in mind that with this system I m adding the other components power too, which included, I combo drive, 1 HD, 2 Ram modules, no monitor, 1 GFX card, (6600 level), 2 case fans, usage may very depending on various other components used.

2. ### Keith SebastianNew Member

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Nice work. Deserves a sticky.

-Keith

3. OP

### gxsauravGuest

thanx, if only the mods can make this & the AMD Cool & Quite thread a sticky, it will help a lot of peoples

4. ### YamarajThe Lord of Death

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And then, there are other important factors like efficiency, PFC, dual +12V
rails and total Ampere rating on +12V. It's true that even a fairly powerful
machine by modern standards will never draw 500W of continuous power,
SLI being an exception case. However, many tend to ignore or forget that
no SMPS comes with a 100% efficiency rating. Established branded PSUs
have efficiency rated from 75% to 85% at most. On the other hand, less
reliable ones of the like sold in our country may not even reach 60% of
their rated output in Watts.

So, if any given configuration needs 300W of continuous power, it's better
to go for an SMPS with at least (300/0.75 = 400W) of power, in case of
branded ones like Antec, Cooler Master etc, and (300/0.6 = 500W) rated
from those of PowerSafe and Zebronics made.

Active PFC is available in quite a few power supplies. Antec have them in
their NeoPower and Phantom models. Cooler Master Real Power 450 and
550W come with Active-PFC too. This Power Factor Correction is required
in EU, and helps in saving overall power consumption by the electronic
equipment.

Dual +12V rails are part of the new ATX 2.0 specification, as is the 24-pin
ATX main power connector. The provision of dual +12V rails is made to
split the power load of the Processor, the graphics unit and others to two
or more different +12V rails. This ensures more reliable operation of the
power supply in case of extra power demanded by some other component
of the machine.

Most ATX 2.0 complaint PSUs come with two or more +12V rails, with Amp
rating of 18 each, in most cases. The ATX specification asks vendors to
split the rails when one is sufficient for 18A of power. However, some PSU
makers don't 'exactly' follow the standard. Some vendors have even split
the +12V rails into two, rated 12A and 8A respectively.

Given today's power requirements, it's best to go for a reputed and well
known PSU brand. After all, a well built machine is of no use if it can't be
delivered the power it needs. For a well loaded Pentium4 or AMD Athlon64
machine, one needs a 450W PSU from Antec/Cooler Master with +12V
rated 25A on single rail or 30A on two split rails.

Recommended: Antec NeoPower, SmartPower 2.0, TruePower 2.0, Cooler
Master RS-450-ACLY, RS-550-ACLY

- Yamaraj

5. ### mohitThe Hardware Labs

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good useful thread , gr8 stuff gxsaurv and yamaraj. my vote also goes to make this one a sticky.

6. ### rockthegodDark Overlord !!!

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real useful stuff gxsaurav.... many ppl who r confused about the ins and outs of the SMPS PSU will learn and make better decisions while assembling their systems... from your simple and well laid out article.

7. OP

### gxsauravGuest

in that case, yamraj, I will suggest U take a look at the 400U model found on colorsit website, & check the amperes ratings given there, this model is available for 1k here, let us know here, is that a good SMPS, with good enough power on each rail

8. ### KHUBBUNew Member

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Nice ,good and informative post. I wud have repped u both if the option was available on this forum.

My vote for making this sticky.

9. ### YamarajThe Lord of Death

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Honestly, I wouldn't recommend this PSU to anyone with a fairly powerful
Pentium4/Athlon64 machine and 6800/7800 PCI-X video card.

This PSU, the Colors-IT Golden Silent 400 model has a single +12V rail
with only 16A in total. While this rating is not sufficient to power high-end
systems, it can well be utilized in average configurations with graphics
cards of power rating 75W or lower. If this PSU has 75% efficiency, which
I highly doubt, it should be able to supply 280W of continuous power.
An important point to note is that power rating of the power supply drops
sharply with an increase in its working temperature. Most power supplies
come power rated at 25C, and drop in efficiency may reach as much as
5 to 10W per C.

To play safe, one should opt for power supplies with no less than 18A on
+12V in total, even for average system configurations.

- Yamaraj

10. OP

### gxsauravGuest

hmm, u better check this out, taken from colorsit website for the 400U Model

+12V = 25A
+5v = 35A
+3.3V = 28A
-12V = .8A
-5v = .5A
+5V SB = 2.5A

a total of 592W, & even if we assume that it is 75% efficient it gives a power out put of true 445W, isn't that enough for a non SLI system

I m not saying that Colorsit is best, i m simply saying that colorsit is a really good alternative to Antec, VIP or Powersafe if they are not available

11. ### YamarajThe Lord of Death

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How exactly did you calculate?
It's a 400W model, hence the name 400U. Total wattage can be calculated:

+12V * 16A = 192W
+5V * 25A = 125W
+3.3V * 25A = 82.5W

A total of (192+125+82.5)= 399.5W or 400W.

- Yamaraj

12. ### zombieResident Weapons Expert

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Thank you guys. I already feel enlightened.

13. OP

### gxsauravGuest

go check that page, silent power 12 cm

that the specs for that, we are getting confused, u r taking a different power supply in account, I m talking about M400U Model which is rated at 600W by the company, likewise the M330U is stated as 450W by the company

don't go for power with model numbar, they are different

14. ### YamarajThe Lord of Death

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All I can see is 400W max PSUs: http://www.colors-it.com/powers.php

- Yamaraj

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16. ### YamarajThe Lord of Death

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Ah! Why do they have two different sites with conflicting info? Grr!
Saurav, thanks for the new link. This site definitely has listed some better
power supplies from Colors-IT.

The specs of the Silent Power 12CM Fan are:

+12V * 25A = 300W
+5V * 35A = 175W
+3.3V * 28A = 92.4W

A total of (300+175+92.5)= 567.5W, which is pretty good even for SLI
systems. 25A on +12V is more than sufficient for most systems, but it
may not be enough for very high-end configurations like FXs or dual
cores with 7800GTXs in SLI etc.

Still, this is a powerful power supply for sure, and if it's available at a price
lower than those of Antec SmartPower series, it's a steal.

Do you own a piece, Saurav? What are its full specifications? How many
and which connectors does it come with? Do a full review man!

- Yamaraj

17. OP

### gxsauravGuest

i myself have a Antec truepower 430W, which i baught 2.5 years ago

however, I have given 2 colorsit SMPS to a few friends in their PC

1st one is M300U-PNU Satnderd, with one exhaust fan 80mm

2nd one is M330U-PNE, 12cm Silent Fan, one 12 cm silent fan below the SMPS, above the CPU

the M400U-PNE, costs Rs 1150 here, but with some negotiation it can be baught for less, it is dam heavy I must say, as an estimate by my own, i say it's about 900 to 1 Kg, although it's just my biceps, weight could be less

All of them come with 24-pin connector for motherboard, with a 24 to 20 pin convertor, 1 SATA Power connector, 4 molex connectors which are splitted in 2 connectors each rail, one standerd 4 pin 12v connector, & the M400U also comes with a 6 Pin PCI-E gfx card connector

true to the name Colorsit, the Power supplies comes in different colors, like blue & red

Colorsit also makes LED Fans & Tubes, since today is sunday, I will enquire tomorrow in the market weather I can get a light tube, U know, this will "spark" things Up

I recomend anyone to go for atleast the Colorsit M350U Silent Power 12 cm model, not only it's silent, it gives

+12v = 20A
+5V = 30A
+3.3V = 20A
etc adding the -12v rails too gives about 480W claimed, at 75% efficiency that about 370W, True power.

anyone wants pics of the side of the PSU for easy finding

18. ### zombieResident Weapons Expert

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This is a quote I picked up from www.slizone.com . Its under the aegis of Nvidia and deals with issues related to SLi.

The dude has AMD Athlon 64 FX55 // DFI LANPARTY nF4 SLI-DR // 2 BFG 7800 GTXs. So he was advised to get an SMPS that can supply 30A from +12V lines. Do we have any SMPS able to meet that criteria ???

19. OP

### gxsauravGuest

u can look for antec truepower 2.0 450w

20. OP

### gxsauravGuest

u can look for antec truepower 2.0 450w