Considering dual PSUs...

Farinorco · Post by **Farinorco** » Sat Feb 16, 2008 5:28 am

Yes, I know that now is when people begins to blame to me because of the absurd overkill of using not one excesive PSU, TWO PSUs!

Little explanation: I'm trying to build a quiet and strongly overclocked (with watercooling) computer. My design makes use of a giganormous radiator of 52x13,5x5,5cm -approx., 3x Scythe Ultra Kaze 1000 (maybe regulated in a near future) sucking from the rad and blowing on the mobo and hds, and a really quiet pump, in a custom designed mdf/melamine case (see my post in the "Cases and Damping" subforum if you want) with 20mm thick synthetic open cell noise damper and indirect air intakes, so it's not gonna be as bad as it sounds when I first said "strongly overclocked"

My rig could be upgraded with a RAID configuration and/or a dual graphic card in the future, and with the overclock, could end up consuming a lot... yes, I know, never so much as to need 2 PSUs

The fact is that in my custom design case, there is room for a dual PSU system without problems, and 2x Corsair VX450 would be 120â‚¬, and 1x Corsair HX620 would be 133â‚¬...

Pros of 2x VX450:

* Cheaper option (!).
* Lots of headroom for future upgrades (900W instead of 620W).
* Highly unlikely that the fans would go up from ~4v even at full loads.
* AFAIK, more silent fan at minimun in the VX450 than in the HX620.
* Halved difference between idle and full load, so presumably less volt drop in low to high load transitions.
* More fun (I'd have to do a little basic electronics with a relay and some wires to start up both PSUs).
* More freak (if having a dual PSU computer is not freaky...)

Cons of 2x VX450 (pros of 1x HX620):

* Only ONE PSU and PSU fan, even if it's a little bit louder (or much if it ends spinning faster because of high load).
* Maybe a weakened voltage in the 12v rail of the 2nd PSU in the dual system because of the low 3.3v/5v load (I've seen that in the extreme case, 2-3A in both 3.3v and 5v, and 33A in the 12v, result in a voltage of 11.71v instead of the otherwise normal 12.12-12.14v, but I'd never really use that 33A load...)

What do you think about it, specially noise-wise (your true speciality

)? Consider a max. load of 400-500W, and a PSU/s place in the back of the case, taking air from a ducted near front (but indirect) intake.

My main problem is that I can't imagine how it would sound one or the other, because I've never heard a Corsair. I'm used to the crappy PSU from my 3-4 years old Dell Dimension, noisy at idle, noisier at full load...

Lots of thanks for any help given to me here

scdr · Post by **scdr** » Sat Feb 16, 2008 10:13 am

Consider a max. load of 400-500W

What are you going to put in there that could take that sort of load in a quiet computer?

Farinorco · Post by **Farinorco** » Sat Feb 16, 2008 10:54 am

Highly overclocked quad Q6600, one (maybe two) overclocked 8800gt, at the moment only one hdd but possibly a RAID in the future, 2 optical units, and of course, the overclocked and overvolted motherboard.

All of that watercooled, using a quad fan radiator, with only 3 fans (instead of 4) at 1000 rpm (possibly regulated) sucking air from it, and blowing on moderboard, pci cards and hdds. Custom MDF case with dampening. And a quiet pump like a DDC3.1 with top or so.

You see, 3 fans at 1000, a quiet pump, and PSU/s as noise sources, but very power hungry components (with all the overclock and so). Maybe not a silent pc, but I think it could be a quiet one.

mcoleg · Post by **mcoleg** » Sat Feb 16, 2008 9:08 pm

that's nowhere near 400-500W so far. what do you have your quad overclocked to and at what voltage?

jaganath · Post by **jaganath** » Sun Feb 17, 2008 2:40 am

probably the only time i will recommend dual PSUs. 2 VX450s for the price of 1x HX620? has to be done, right? load on each PSU will be so low (~150W each) they should be inaudible.

Farinorco · Post by **Farinorco** » Sun Feb 17, 2008 5:36 am

mcoleg wrote:that's nowhere near 400-500W so far. what do you have your quad overclocked to and at what voltage?

I don't really know how you can be able to guesstimate nothing with the (intentionally) incredibly vague specs I have given there

Don't misunderstand me, I don't want to tease anybody here (you are helping me!), it's just that I'm near completely sure that I'll buy a quad, a 8800gt, just one hd right now... but I'm also near completely sure that I will change my graphic card in 1-2 years, and sooner or later I'll try an array of more than 2 drives in RAID (more sooner than later). I believe it's not the time of multiple GPUs by now, but I strongly believe that this is about to change in the near future...

Look at this:

jaganath wrote:probably the only time i will recommend dual PSUs. 2 VX450s for the price of 1x HX620? has to be done, right? load on each PSU will be so low (~150W each) they should be inaudible.

These were my exact thoughts when I saw that VX450 was around 60â‚¬ and HX620W around 130â‚¬ where I live.

If I'd be confident that a single VX450 can handle a highly overclocked quad, an overclocked gt, and the rest of the computer, without making much noise when fully loaded, I'd buy one right now, and then, if necessary, the other. But I don't think so. And buying a PSU that costs the same or more than the other two, defeats the whole point of the idea...

At the moment, it seems that jaganath gives a vote to the dual VX450

Do you see any reason not to go this way, either noise-wise or other?

Thanks for your help and interest to anybody here

mcoleg · Post by **mcoleg** » Sun Feb 17, 2008 8:31 pm

i overclock.

the main power draw will come from the quad and from the vid. card. i've gtx. gt's are not as power-hungry as gtx but i could make an estimate. the cpu's draw will depend on overclock. "strongly overclocked" might mean many things but if you throw in "quiet", your clock will have certain limits that could be approximated, water or not.

normally when i see an overclocked quad with sli or crossfire, my recommendation is to go crazy on the psu and buy as big as you can afford. but looks like right now you are overshooting, just a touch.

anywho, what's "strongly overclocked" for you?

Farinorco · Post by **Farinorco** » Mon Feb 18, 2008 3:16 am

mcoleg wrote:i overclock.

the main power draw will come from the quad and from the vid. card. i've gtx. gt's are not as power-hungry as gtx but i could make an estimate. the cpu's draw will depend on overclock. "strongly overclocked" might mean many things but if you throw in "quiet", your clock will have certain limits that could be approximated, water or not.

normally when i see an overclocked quad with sli or crossfire, my recommendation is to go crazy on the psu and buy as big as you can afford. but looks like right now you are overshooting, just a touch.

anywho, what's "strongly overclocked" for you?

I don't know, I've never used water, and I'm gonna buy a quad radiator that I will use with 3 fans, in my head this should make the rad much less restrictive to air given the increased surface to each fan, so chances are that with low speed fans (1000 rpm by now) its performance will be near a quad radiator with 4x fans than a triple radiator with 3x fans with no much noise (specially if the 3 fans are gonna be the only fans in the case, aside PSUs, as it's gonna be the case in my custom design case -they will blow on MB and HDs after suck air from rad). Probably a Fuzion or MC-TDX, MCW60R, and probably a MCP350/DDC1 with Alphacool top. I've not decided about NB cooling yet (water, stock or what).

I supose that all high that my future system allows me to run 24/7 stable without going over the thermal specifications given by Intel

Of course I'm talking about 24/7 overclocks. I'm not interested in any kind of benchmarking or so.

Anyway, my estimation of about 400-500w was in the case of the OCed quad, the OCed SLI/CF, and a RAID of about 4 HDs. I know my starting rig would be consistently less power hungry than that. I just want the needed room to add those things if I decide to go with them along the next 1-2 years without having to change the PSU/s...

Do you think that guesstimation of mine is more or less realistic? And also, do you think there is any reason to not go the dual PSUs route that I've not thought before? I'm interested in your opinion regarding this...

mcoleg · Post by **mcoleg** » Mon Feb 18, 2008 9:07 pm

here's what concerns me - you'll have 3xslipstreams at 1000rpm, 2xadda in the psu's and a water pump. i am not even counting chipset cooling, which you'll need if you go with nvidia board and 2xvideo card coolers. this is not going to be anywhere close to "silent".

the system i am playing with now has the same psu as you are looking at, e8400 @ 4Ghz (i am not even trying to push it so i can keep the cooling very quiet) and 3870 video card (with undervolted fan).

i tried two slipsteams at 1000 rpm in it. together with the psu, they were making way too much noise. the point being - that combo by itself is not quiet, it needs to be tweaked. i had to bring the fans down to about 6-700 rpm (4-500 rpm idle); then i swapped the psu fan (couldn't stand the noise it makes). now it's more or less reasonable.

so, you'll have a choice to make - less noise or higher clock. if you really want a quiet system, you'll have to drop the slipstreams to at least 600 rpm and undervolt the pump to around 9v. that would limit the clock considerably.

VX450 are not that pleasant to listen to from my experience. if they are the main source of noise, as it was in my case, they are pretty annoying. fan-swap helps though.

as i said before, if you overclocking quad and planning on sli, might as well get as much power as you can afford. you might hit around 400w actual if you overclock the vid. cards. 2xpsu's is as good option as any. it's just if you want silence, your clocks might not be as high as you planned and thus the power draw would be less proportionately.

btw, why not wait a bit for new 45nm quads? might get a better clock out of them with less heat and less power consumption.