Guide Choosing the Right Power Supply Part I – Calculate the amount of power you need

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Choosing the Right Power Supply Part I – Calculate the amount of power you need
Scenario :

You just got that droolmaal rig you have been saving for, now you need to figure out which SMPS/PSU you need to power this thing.
Don't, I repeat don't think that getting a cheap PSU is a good idea, people spend over 10k just for the Motherboard and CPU all to get a 450 bucks SMPS in the end.
Consider this, if CPU is the mind of the system, the SMPS is the heart of the system, it provides the power needed to keep the CPU going on. Now why would anyone want a high and brain and skimp out on the heart.
As phoenix said here

http://www.techenclave.com/forums/things-know-before-buying-perfect-graphic-92235.html
Nowadays , cards requiring you to have at least a good high-wattage PSU like a 600W-700W are there which just will refuse to run on older supplies, or if they do, serious problems like heating and burnout of the GPU can happen. So before yu buy a card, make sure you check its power requirements , and get a PSU which is capable of providing at least equal to, or more than that requirement if you want to keep your card running at full potential. Always compare the Amperage of the PSU and see if it meets the requirements, and always get a good reputed PSU , coz there are lots of supplies out there, which show good Wattage output on the outside, but are nowhere even close to what they claim . Good supplies are Corsair, OCZ GameXtream, Coolermaster etc.
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Also, some people have this notion that when you buy a SMPS of high power rating say 600W it will consume 600W all the time. This in NOT TRUE, a SMPS consumes only that much power which is required at that particular moment by the system.
When asking for recommendations for a new Rig/PSU I recommend that one goes through this article and mention the power requirements in the new thread.
This guide will help you calculate the maximum power your SMPS needs to have to provide stable operation to the system.
Consider the following components :
  1. CPU
  2. GPU
  3. Motherboard
  4. HDD's
  5. DVD RW's
  6. Fans
  7. Other LED's etc
Note : We will be considering power required at extreme loads as this is what the SMPS must be able to provide when needed, the PSU can always provide lesser power when required.



Lets discuss all these components in detail :
[BREAK=Power of each component in detail]

1. CPU :



CPU's these days have a TDP (Thermal Dissipation of Power) at about 65W for the mid end and go up to 150W for some high end processors (Current Quad cores). These ratings, keep in mind are absolutely high end readings and the processor may or may not consume this much power at load.



If however you do Over Clock the system, the maximum TDP increases, heres how to calculate the TDP of a OC'd system.



Overclocked TDP = Current TDP * %age of overclock + Current TDP * %age increase in Vcore



Example : Consider a E4300 rated at 65W running at 1.8GHz stock with default Vcore at 1.25V



When OC'd to say 3Ghz at Vcore 1.4V thats



%age of Overclock = (Current OC Speed / Default Stock Speed)

%age increase in Vcore = 1 – (Current Vcore / Default Vcore)



That means :



%age Overclock = 1.66



%age Vcore = 0.12



Which means :



Overclocked TDP for this example becomes = 65*1.66 + 65*0.12 = 115.7W



You can similarly calculate the Power requirements for any other processor by knowing these simple variables (hint : Google for the TDP of your processor)



2. GPU

 This is a tricky part as power required by the GPU's increased with every new generation of graphics cards, basically I'll list the TDP of some of the common GPU's bought today and the Overclocked TDP can be calculated in a similar manner as above. For TDP of other GPU's use Google. Always remember Google is your friend.



Disclaimer : These rating are approximate



nVidia :



7900GS : 110W

8500GT : 40W

8600GT : 75W

8600GTS : 110W

8800GTS : 150W

8800GTX : 180W



AMD/ATI :
HD 2900XT : 200W



If using more then 1 card using SLI/Crossfire Technology, add the TDP of both the cards.



If some one knows TDP of more GPU's mention in the comments section and I'll update the article accordingly :)



3.Motherboard

This is a tricky part, couldn't find information on the TDP regarding the motherboards and then I read this :



Intel 8-core Xeon X5365 V8 Performance Preview



You’re looking at about 75W for the motherboard, case fans, keyboard/mouse, USB hubs, etc.
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Since I am covering case fans later onwards, for a motherboard add 60W of Power.

4. HDD's

For each HDD you have connected to the system add 15W at load.



5. DVD RW's

 For each DVD RW you have connected to the system add 20W at load.

6. Fans

 For each high speed high performance 120mm fan add 10W



For each high speed high performance 80/92mm fan add 5W
For other fans connected the system add 2W



High Speed High Performance fans also include fans installed with the SMPS, CPU and GPU.



7. Other LED's etc

For these add some 15W in general.



[BREAK=Final Words]

Final Words :



Calculated the total power supply you require, now increase the same by 20% for PSU degaradation over time and 15% for future upgrades (or calculate the future power upgrades manually).



The final wattage is what the PSU you get should have at the bare minimum for a stable, smooth and tension free operation of your system.



Other part of the series coming in a few days.



Comments Welcome. :ohyeah:

[BREAK=New Addition : A Few Examples]

Consider a very very High end rig

Core 2 Duo E6600 @ 3.6Ghz 1.4V Vcore = 105.3

XFX 680LT = 60W

8800GTX*2 in SLI = 360W

4GB RAM

500*2 GB HDD = 30W

LG H42N DVDRW = 20W

2 120mm fans as exhaust = 20W

1 120mm fan on the CPU with TR 120 Ultra = 10W

Total Power Consumption = 605W

Add some fudge factor (35%) for PSU degradation and upgrading possibilites (20+15) = 211W

Total PSU Wattage you should be looking for 816W continuous at 50degrees

Consider a mid end rig :

Core 2 Duo E4300 @ 3.4Ghz 1.4V Vcore = 130W

XFX 650i Ultra = 60W

8800GTS = 150W

2GB RAM

500*1 GB HDD = 15W

LG H42N DVDRW = 20W

1 120mm fan as exhaust = 10W

Stock cooling fan on GPU = 10W

Stock cooling fan on PSU = 5W

Total Power Consumption = 400W

Add some fudge factor (35%) for PSU degradation and upgrading possibilites (20+15) = 140W

Total PSU Wattage you should be looking for 540W continuous at 50degrees

Consider a low end rig :

Core 2 Duo E4300 @ 1.8Ghz 1.4V Vcore = 65W

XFX 650i Ultra = 60W

8500GT = 35W

2GB RAM

250*1 GB HDD = 15W

LG H42N DVDRW = 20W

1 80 mm fan as exhaust = 5W

Stock cooling fan on GPU = 5W

Stock cooling fan on PSU = 5W

Total Power Consumption = 210W

Add some fudge factor (35%) for PSU degradation and upgrading possibilites (20+15) = 74W

Total PSU Wattage you should be looking for 284W continuous at 50degrees
 

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Nice guide but a bit incomplete. Now why not take a test system with a C2D and so & so setup and then calculate its power requirements?
 
Deepak nice compilation...but get a DMM & wattmeter(if possible) and see the readings in ur PC....u will be amazed to see how much it differs frm the specs listed on the components. Trying out various PSUs will also help :P
 
Yeah, I kno that they do vary and are usually the power ratings are very very less then this, but the point is that this is the *MAX* a PC will consume, and a PSU needs to be able to deliver under this load condition without breaking a sweat....
 
Hey... Is possible for you to relate this to the UPS power needed for various back up Time Required ?

Will add even more value to the article.
 
Review of local brand Frontech, Mercury, Zebronic all low cost PSU in the range 400 to 600 review with pros & cons will help lot to lower end pc. which is need of the hour.
 
Hi ,

Suggestion ,first my Compliments Nice Article ,Secondly Make a Excel File with The Formulas ,Will Help the Users ,Third The 120mm Fans Consume 5 Watts Mostly .
 
gcbeldar said:
Review of local brand Frontech, Mercury, Zebronic all low cost PSU in the range 400 to 600 review with pros & cons will help lot to lower end pc. which is need of the hour.
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They are crap- stay away from them for your own good. :hap2:
Trying to review them to discover/prove any nonexistent goodness is like trying to win the Derby with a buffalo. :D
Helped you in the need of the hour- what do i get?? :P
 
ComradE_BeaN said:
^a proper review of Zebby/Delta 500 Server PSU would be good. :)
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That was for 1500/- iirc?? :)

I think gcbeldar wants someone to review frontech/mercury/zebby in the Rs.400/- to Rs.600/- price segment. :rofl:
people can buy better gfx cards, better cabinets, mice, mouse pads, ...- but will always compromise on psus for soem weird reason- maybe coz the benefit is not so visible. :S

If one cannot invest 10% of a rig's cost towards the most crucial component that powers the whole setup, they don't deserve a PC imho. :cool2:
 
BIKeINSTEIN said:
That was for 1500/- iirc?? :)
I think gcbeldar wants someone to review frontech/mercury/zebby in the Rs.400/- to Rs.600/- price segment. :rofl:
people can buy better gfx cards, better cabinets, mice, mouse pads, ...- but will always compromise on psus for soem weird reason- maybe coz the benefit is not so visible. :S
If one cannot invest 10% of a rig's cost towards the most crucial component that powers the whole setup, they don't deserve a PC imho. :cool2:
Click to expand...

ppl say zebronics etc... are crappy, but on what grounds?? Even I support the requirement of a proper review :)
 
booo said:
ppl say zebronics etc... are crappy, but on what grounds??
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One doesn't have to be very smart to know this- just some trust on senior people and colleagues, esp those with first hand experience who mostly don't lie. :)

First hand experience is the best teacher though irritating, heartbreaking and cosly to mend at times. :P
Read up on how and why psus are termed good. :)

Read up on how or why the so-called bad psus are bad/risky and what risks they pose to hardware.
Google for psu models from the brands u interested- check up their oems.

Check remarks/comments abt that particular manufacturer wrt components, quality of componenets, purity and stability of o/p signal, etc.

Google for the psu models u interested- and Google just might throw up a list of issues some might have had with that certain thing.

So on and so forth. :P
If you find out- post your list of observaions/discoveries and title it as a review. :lol:
 
:)^^ Bikey..I do know that these bad psus are ...well mostly bad(after joining TE)...:P

However I have a question..

During our college days everybody used standard components for their pc's (barring graphics cards ) and they obviously had generic psu's...

Very few (CS branch say 70 guys +Info SC another 70) psu's actually conked out and most of the systems ran well for 2 to 3 yrs...:rofl::rofl:

How ? Or are generic one's okay for generic systems?

Just curious ?

p.s I did spend 5.5 grand on a decent psu so do not support cheap psu's anyways
 
An old thread suddenly revived after a long time...

@raj_pol : It depends on your rig's power eating capabilities. If it doesnt require more then say 10A 200W then a generic one would last you for 1-2 years depending upon usage.

Usage here depends upon how much time you are running your system.If its a 24x7 rig then the PSU will degrade more rapidly (local ones more so then others). Also depends on what kind of stress you are putting on your rig. If your CPU/GPU/HDD utilization is 100% all the time; again that puts more stress on the PSU.

In the end, it all comes down to the quality control the PSU went through and the kind of power ratings it can support.

Hope most of what I said was correct :ohyeah: now-a-days all I have time to think of is work-work-work :@ so mind tends to get a lil rusty :bleh:
 
Hi ,
I Would Like To share My Experiences in repairs Of The Same .

See this diagram .



See In All The Low cost SMPs No Magnetic Ferrite is Used ,Also All The Components Like The SMPS Master Capacitors Are Poor Quality ,Good Brand Are nippon Chemicon ,Etc .
 
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