Power Supply Basic Facts.

[xeromist]

The calculator is a good talking point but I wouldn't rely on it completely. In some cases it's going to go way overboard and in others it will fall short. I put in my old c2d system with tri sli and it's recommendation using "recommended" settings is a 604W PSU. I saw that system peak at 700W at the wall. In other cases you guys are posting smaller systems with bigger estimates than I've seen people use 24/7. Since we don't know how they got all of those numbers it seems hit or miss whether it will be accurate.

[Zka17]

That's what I'm saying! Whenever we are posting some wattage value, we should automatically mention if it's an estimate or a real/measured value. With the real/measured values we can not really argue... Then we can discuss how to estimate values - and here may be helpful if people would start posting the estimate values of their system together with the real values. After a while we could get a picture how these estimates are working...

[Kipper]

I didn't see anyone discussing AMPs so far.

I have always added up the draw of my components and then make sure the 12V rail is more than sufficient for the components I am using and a little room for upgrades down the line.

For all the PSU reviews I have done over the years for most of the big boys; TT, Corsair, Seasonic, Silverstone, Enermax and most of the rest of the big boys I would load up the test bench with some power hungry components and while stressing the system with a nice OC and hammering it with Prime and furmark and then monitoring the 3, 5, and 12v rails.

Haven't done in PSU reviews for a year or so now but still use my tried and true testing which can be done with an inexpensive multimeter.

Here are links to a couple nice units I reviewed last year.

High Power Plus Gold 1200W

Seasonic X-series 850W

[Zka17]

Wow, Kipper, nice power supplies you reviewed there! Somehow I never came across those... but I will keep them in mind!

"I didn't see anyone discussing AMPs so far." - you're right, we didn't get there yet... From my part, the reason is that I don't feel 100% sure if I've got the idea of single vs multiple rails...

Could somebody elaborate more on this, please?

[DaemonCantor]

Zka17, did you read the post where I described how a PSU works? If not take the time and read it.

The Second Stage there is where your Power RAILS come out and what they do is instead of one Voltage Regulator(Single RAIL), they use up to four cheaper ones(Four RAILS) and divide the current across all of them. An AMP is still an AMP but now instead of like 70amps coming from one RAIL you now have that 70amps divided between up to 4 RAILS or 70/4=17.5amps each which gives Voltage times Amperage = Watts or 12v*17.5amps=210watts per RAIL on a 4 RAIL system but now you also have to take into consideration of where the 5v is coming from and that's the 12v RAILS so now you loos that extra 10watts per RAIL to the 5v line and end up with 200watts per RAIL. Your 3v is still seperate so that's not even a consideration at this point.

I hope this explanation is easy enough to understand.

[XZEMi]

XZEMi, based on "Compared to Corsair and Seasonic this power supply remained cool to the touch under all loads. It was perfect for my mini atx case because its fan constantly evacuated heat from the case." - let me guess: your mini atx case was one with a top-mounted psu. Otherwise I could not understand how any psu can get hot to the touch...

With the top-mounted psus which draw air from inside the case is one major problem: they are sucking in the naturally rising hot air produced by cpu, vrm, north bridge, graphic cards, etc. That is the reason why most of the manufacturers switched by now to bottom-mounted psu designs. If the psu is placed on the bottom, it means that is supplied with the coolest air we can find in a tower case - this in case if the psu sucks air from inside. But, most manufacturers today went even further and they are designing their cases with separate thermal zones - the psu draws air from outside (through bottom vent hole often equipped with filter) and exhausts outside. This way the psu is in the coolest place and won't contribute anyhow to the system's overall temperatures.

In conclusion, when designing a new built, it is very important to clarify the placement of the psu - and choose your psu accordingly.

Side mounted over video card.

http://www.amazon.com/Lian-Li-Tower-.../dp/B0057BSGJ4

Lian Li PC-V354

[chrsplmr]

Kipper .. I got to say .. boy when I am wrong it is a doozy ... This thread is awesome.
Thank You All... ooops. (Sorry it smelled funny and setOff my FlapOmeter .. I was wrong.)

... The only thing I enjoy more about this forum than helping someone is all the opportunity to learn.
Look Ma, Im learning .. No hands.

.. sorry to interrupt .. please, continue ...

[Zka17]

Nice little case, XZEMi! One that cry after modding right as you got it...

One of the first hits I google it was this review: http://xsreviews.co.uk/reviews/cases/lian-li-pc-v354/

Even there is mentioned what sticks to my eyes: the PSU is drawing air from the VGA. Now I understand why are you concerned about the PSU’s temperature! I didn’t found this a great idea... In some circumstances the VGA may be the hottest component in your system, cooling it with the PSU... – well, that PSU wont last too long (and lucky if the PSU is dying only by himself and is not taking some other components with too).

So, my idea is to invert the PSU with it’s intake toward the side panel. Then cut a big hole on the side panel accordingly with the PSU’s intake. I suggest you to put some dust filter over it – then you will stop worry about PSU’s temperature forever!

[Zka17]

DaemonCantor, I have to confess that I didn't get 100% sure how the PSU works from your previous post (#23)... - since then, however, I did my homework and read a lot about, and now with your second post (#35) starts to get clearer and clearer! Thank you for leading me in this process! BTW, you didn't comment on my post #30 - I'm extremely curious how you would explain the discrepancies...

Just to conclude for myself (please correct me if something is still wrong): Rails are practically voltage regulators. Regarding the output, there are at least 3 rails/voltage regulators - one for each of 12V, 5V, 3V. Number of rails/voltage regulators depends on the quality of components used - cheaper ones has more, performant ones has less. The amperage on each rail is determined by the manufacturer/way how the transformers are designed. Is this right until this point?

Now let's take two supposedly high end PSUs: Corsair AX1200 and Silverstone ST1500 (choosed these because I own them, and they are perfect for the reason of this post - yes, I know, they have different efficiency ratings). I prepared a table with their voltages, amperages and wattages:

Attachment 8265

Now, my question is: For an average system builder, which design suppose to be better - single or multiple 12V rails? In case of two PSUs with the same efficiency ratings the single rail would only mean higher quality? Would there be arguments for using multi-rail ones?

What I see from the Silverstone's specs: although it has eight 12V rails each rated at 25A, the max combined load can be only 110A (instead of 8x25=200A) - why?

[DaemonCantor]

Zka17, Your answer to post #30 was done by xeromist but let me go a little further in I don't hold stock to the Calculators because on many occasions I've used them multiple time with the same exact info only to get scores all over the place plus they differ from site to site so how can you be sure if 981watts is correct when the next person gets 575watts and then you go back and get 692watts and then you go to NewEgg and get 1192watts... I see no real value except for comedy.... Really think about it, how in the hell could a system that takes 350watts just to fire up with out a Video Card need only a 550watt PSU with a card that requires 180watts from the system bus. That only leaves 20watts for when the system goes in to High Performance like playing a game...Wow I can see a lot of people buying PSU's every time they play Crysis! Now remember the link I posted on the power of the 5870 that same system would need a 350watt + 354watts = 704watts minimum with out any room for possible extra power but you still have to add that into it and like I was saying you need a minimum of 30% for reserves which in this case is 212watts so now were at 704w + 212w = 916watts. Like Kipper stated basically 'Do the Math!'.

Ok your getting a clearer idea but on a Single RAIL design it doesn't have three RAILS(12v, 5v, 3v) it has two RAILS a 3v, and the 5v and 12v are one in the same RAIL.
On that Silverstone PSU 200a - 40a(+5v) = 160a - 63a(-12v & +5vsb) = 124a - 14a(reserve) = 110a ... Tey are giving the Power output off the Primary Stage 'Calculated' instead of the Secondary(Output)stage and a easy way for them to cut Cost in Production because they don't have to give a single bit of extra power like Higher Quality Units... Like I stated Higher Price Doesn't mean Higher Quality!