The Power Supply Thread


dgaschk

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  • 4 weeks later...
  • 2 months later...

It's been mentioned in this thread and else ware around the web that Seasonic will provide extra cables if requested. I wanted to give an update that if that was true in the past it no longer is true today.

 

I contacted their customer service department and requested a couple more molex cables for my 26 drive build using their SS-760XP2 PSU. They asked for me to send them my proof of purchase, and after I did they told me I would have to buy any extra cables from a third party. Why they needed my proof of purchase To tell me that I'll never know.

 

I really like their PSU's and have never had any failures or issues with them, but I wanted to let everyone know they shouldn't expect free cables from Seasonic going forward and to factor the $7 or so per additional cable (plus shipping) into the price of the PSU. Not a big deal, but something to be aware of.

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In regards to power supplies I found the Rosewill PSU RD600 600W RT was nice for the price but the limitation came in form of eight sata power plugs and 4 molex power plugs. If I have 15 (non-powered cages are 5x3) drives how can I extend the plug usage to meet all 15 now that also has to include powering the fans too. I can daisy chain the fans together to be used on two molex connectors. I have look through the power supplies listed and most are limited on numbers of connects. Is there something I can put on the cages to loop the power to each drive? Any suggestion would be nice.

 

Thanks

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In regards to power supplies I found the Rosewill PSU RD600 600W RT was nice for the price but the limitation came in form of eight sata power plugs and 4 molex power plugs. If I have 15 (non-powered cages are 5x3) drives how can I extend the plug usage to meet all 15 now that also has to include powering the fans too. I can daisy chain the fans together to be used on two molex connectors. I have look through the power supplies listed and most are limited on numbers of connects. Is there something I can put on the cages to loop the power to each drive? Any suggestion would be nice.

 

Thanks

 

You'll want to put some splitters on your molex cables to increase the total number of connections. Monoprice is a great place to get those:

http://www.monoprice.com/products/subdepartment.asp?c_id=102&cp_id=10245&cs_id=1024501

 

If you need more SATA connectors:

http://www.monoprice.com/products/subdepartment.asp?c_id=102&cp_id=10226&cs_id=1022604

 

For example, if you wanted to change 1 molex into 2, you could get this for less then $1:

http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10245&cs_id=1024501&p_id=1313&seq=1&format=2

 

Just be careful on connecting a bunch of these to one cable from your PSU. You should try to use all the Molex/SATA cables evenly so that the power is distributed across your cables. I don't feel comfortable with more then 7 hard drives on a single cable from my PSU. Too many devices on a single cable could cause issues as the cable wire itself may not be able to supply enough current for all the devices on that chain.

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Doing the calculations from this thread with my setup:

 

14 green/red drives (14*2) = 28a

10 7200 drives (10*3) = 30a

2 SSD's = 2a? This might be on the 5v rail though.

8 120mm fans and 3 140mm fans = 1.5a

System = 5a

3 PCI-E cards = 3a

2 USB devices = 2 a

 

Adding that all up I'm at 71.5a. A Seasonic 1000 watt PSU has 83a on the 12v rail. The 860 watt PSU is 71a. The 1000 watt would be the safe bet, but wouldn't be as effecient. The 860 watt would be cutting it close. Although, I believe the 2a green and 3a 72000 estimations are already a bit inflated. It seems the greens are usually 1.6-1.8. I've also heard the Seasonic's can provide short bursts of power over their stated specs. If both of those are true, the 860 watt PSU would be my best bet.

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I hope this is the right place to post this question:

 

I have the CX430 PSU (just came in the other day). I see that it has 4 SATA connectors + 3 Molex connectors. Since I'm not planning on any drive enclosure (which would have provided me a backplane for power) I'm assuming I need these to convert those molex connectors to SATA power:

 

http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10226&cs_id=1022604&p_id=8793&seq=1&format=2

 

Also - that page states that

" The Molex connector provides only 5 and 12 VDC power. While many SATA drives only require these power levels, some require the additional 3.3 VDC power provided for in the SATA specification. Make sure your drive does not require 3.3 VDC before purchasing this adapter cable."

 

How do I make sure that's the drives I'm using don't need the 3.3 VDC power? The drives I'm currently planning to use are:

Cache : Seagate Barracuda 7200rpm : 2 GB

Parity : Seagate Go-flex 3TB drive (will take the drive out of the enclosure)

DATA1 : Seagate Go-flex 3TB drive (will take the drive out of the enclosure)

DATA2 : Seagate Go-flex 2TB drive (will take the drive out of the enclosure)

DATA3 : Seagate Go-flex 2TB drive (will take the drive out of the enclosure)

DATA4 : Seagate Barracuda 7200rpm : 2 GB

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............." The Molex connector provides only 5 and 12 VDC power. While many SATA drives only require these power levels, some require the additional 3.3 VDC power provided for in the SATA specification. Make sure your drive does not require 3.3 VDC before purchasing this adapter cable.".................

Conventional wisdom (Googel" says, "no current desktop drives use the 3.3V line." The quote from the vendor is more of a CYA statement. You should be fine! But not knowing the EXACT model number of your drives there's always going to be a tiny room for doubt. So let's say I'm 99.44% sure.

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  • 2 months later...

I admit I'm a little sketchy when it comes to figuring out the PSU.  I understand that I need enough power for spin up and other high demand times, but at the same time I want to hit that 50% sweet spot during the majority of operation, right?  Where I falter is figuring out the math.  Could someone well versed in PSU selection have a once-over on my build and comment specifically on the PSU?  I'd appreciate it.

 

I'm not married to the PSU I've "selected"... but it seems to fit the bill and the price is good right now.  There's a Seasonic available for 300W at the same price, but its a funny form factor so I don't really know how it will work with my case (I believe its meant for 1U servers but its listed on newegg under desktop)

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I want to hit that 50% sweet spot during the majority of operation, right? 

 

No, you're not going to come anywhere near 50% utilization with that build.  I'd guess your typical draw will be in the 60 watt range ... perhaps even lower ... ramping up to perhaps 75 watts with all drives spun up and running a parity check.

 

With only 3 WD Reds, your total drive current is going to be ~ 15 watts ... so I'm assuming about 60 watts for motherboard/CPU/fans -- difficult to say for sure, that should be about right.  If you're running high-CPU utilization transcoding, it will be more ... the CPU alone can draw up to 55w, but even at that you're not going to come anywhere near 50% of a 400w supply (as you've listed)>

 

Note that 80+ certified supplies have to meet the specified efficiency at 20%, 50%, and 100%.  Below 20% the efficiency often drops rapidly.    So what you really want is to run at ~ 20% so you're getting maximum efficiency.    For a 3-drive system, a 300w 80+ PSU would be a very good choice.

 

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Wow, OK... that flies in face of some other advice I got on a different forum (they said I needed 750W "at least").  What you say makes sense though.  I'm kind of an idiot when it comes to power calcs... but I don't think its just me, its the lack of real info.  CPU, for example, they only give you a hypothetical TDP.

 

OK, so you think a 300W is what I should be aiming for then?  Single rail...  I mean, there's this one for only 13 bucks!  But I think even hamsters cost more than $13, so I don't want to trust that I don't think.  I don't see any (at newegg... of course I can expand my shopping horizons I guess) that fit the bill and are a brand I think anyone could trust. 

 

Seasonic has this 360W... where's that put me?

 

Or... is the "single rail" doctrine all that important with a low-power system like mine?  Is it more important to get lower wattage?

 

Help  :(

 

edit:  After I typed this, I saw your post about the 300ES... I was just looking at its datasheet while typing, and saw that its multi-rail, which led me to my above question.

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I want to hit that 50% sweet spot during the majority of operation, right? 

 

No, you're not going to come anywhere near 50% utilization with that build.  I'd guess your typical draw will be in the 60 watt range ... perhaps even lower ... ramping up to perhaps 75 watts with all drives spun up and running a parity check.

 

With only 3 WD Reds, your total drive current is going to be ~ 15 watts ... so I'm assuming about 60 watts for motherboard/CPU/fans -- difficult to say for sure, that should be about right.  If you're running high-CPU utilization transcoding, it will be more ... the CPU alone can draw up to 55w, but even at that you're not going to come anywhere near 50% of a 400w supply (as you've listed)>

 

Note that 80+ certified supplies have to meet the specified efficiency at 20%, 50%, and 100%.  Below 20% the efficiency often drops rapidly.    So what you really want is to run at ~ 20% so you're getting maximum efficiency.    For a 3-drive system, a 300w 80+ PSU would be a very good choice.

 

You don't have to stick with an ATX form-factor PSU...consider SFX as well.

There are 80+ Bronze models from Fortron/Source rated at 200W or 250W, like the FSP200-50GSv or the FSP250-60GHT (edit: this is TFX...check dimensions)

Your planned system would not hit a spike above 130W during boot...maybe 80W at max when fully booted....maybe 30W when idle and disks spun down.

 

...you might as well take the risk and go for 120W pico-PSU...go for a 35W TDP CPU to avoid spikes above 120W....feed the pico with a 135W notebook PSU and you're good to go.

 

Edit: the 250W model isn't single rail, but for 3 disks and a PSU above 10A on each rail, this is not relevant.

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I researched CPUs for days... between price, power and availability I had to, unfortunately, rule out all the 35W options.  The CPU I'm getting has a TPD of 55W or 57W.

 

OK, worst case scenario then... say I get that 360W PSU and Ford's right and my system is only utilizing 30/80/130W.  Then that means I'm at 8.3/22/36% utilization?  I guess I get that is "too low" (especially at idle), but what does that really mean?  @ 20% its 87% efficient, so does that mean at 80W draw, the PSU is pulling 92W from the wall?  Let's pretend @ 8.3% its only 70% efficient... that would mean 30W idle pulls 43W from the wall, thereby "wasting" 13W (am I right so far?).  13W * 8760 (hours in a year) means max wasted is 114kWh... or about $8 a year where I am.  If that "math" is at all reasonable for a worst case... then I'm OK with that.  But if it doesn't tell the whole story, or its worse than I'm supposing....

 

I do get now that I'm better off with a lower W PSU.  Availability is an issue is all.

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Sure, but its still a positive thing.  I mean... a less efficient lower-power system is still going to be a net gain over a more efficient higher-power system unless you're right on the cusp (ie. there will be some overlap).

 

Anyway, I have to work with what there is available to me.  I've narrowed down to these PSUs:

  • SeaSonic SS-300TFX Bronze 300W due mostly to its glowing review at Hardware Secrets (HS).  its problem is form factor.  It won't "fit" in my case... although I suppose I can just make it fit.  I love the price, at $40 inc shipping.
  • SeaSonic SS-300ES Bronze 300W has no review at HS but can I assume it has similar performance?  Its the right size/shape for the case.  Cost is $6 more due to shipping but that's no big deal.
  • SeaSonic SS-300ET Bronze 300W is same as above but with a larger fan.  $61 including shipping.... which is a rather large premium for a larger fan
  • SeaSonic SSR-360GP 360W is the one I'd jump on other than the extra 60W I don't need or want.  Again it gets a fantastic review at HS.  Right form factor.  Gold certified.  $66 shipped.

 

 

I think I'm leaning toward the first one.  Not sure if I should get a new case... or just make it fit in the one I have.  By "make it fit"... I mean, realize that this system is going in a basement utility room so I can pretty much just lay it on the bottom of the case on some foam (for vibration) and not even screw it into anything.

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I researched CPUs for days... between price, power and availability I had to, unfortunately, rule out all the 35W options.  The CPU I'm getting has a TPD of 55W or 57W.

 

OK, worst case scenario then... say I get that 360W PSU and Ford's right and my system is only utilizing 30/80/130W.  Then that means I'm at 8.3/22/36% utilization?  I guess I get that is "too low" (especially at idle), but what does that really mean?  @ 20% its 87% efficient, so does that mean at 80W draw, the PSU is pulling 92W from the wall?  Let's pretend @ 8.3% its only 70% efficient... that would mean 30W idle pulls 43W from the wall, thereby "wasting" 13W (am I right so far?).  13W * 8760 (hours in a year) means max wasted is 114kWh... or about $8 a year where I am.  If that "math" is at all reasonable for a worst case... then I'm OK with that.  But if it doesn't tell the whole story, or its worse than I'm supposing....

 

I do get now that I'm better off with a lower W PSU.  Availability is an issue is all.

 

Your system is not likely to get down as low as 30w.  My atom-based system idles at 20 watts; but the motherboard/CPU you have, coupled with the case fans and heatsink fan is more likely to draw in the 35-40 watt range.  The maximum doesn't really matter -- you'll very rarely draw that (only during high CPU utilization like a transcoding task).    So assume you idle at 35 watts and buy the Seasonic 360w unit.    You'd be drawing ~ 10% of the rated power.  It's an 80+ Gold unit, which means it's 87% efficient at a 20% load.  I'd expect efficiency to drop by 5-10% ... so for illustrative purposes assume it drops to 80%.    At 80% efficiency, drawing a 35w load, that means you'd be drawing 44w from the A/C supply ... a "waste" of 9 watts.    HOWEVER, even if you were operating at the "80+ Gold" efficiency (87%), you'd still drawing 40 watts from the A/C supply -- so the lowered efficiency is really only "costing" you 4 watts of power.  4 watts wasted 24/7 is 35kwh per year wasted ... not sure where you're at, but in the US with an average cost of ~ $0.12/kwh that's $4.20/year.  Clearly not a big deal.

 

The reason a lot of folks use larger supplies is twofold:  (a)  the PSU manufacturers concentrate on their higher-end, higher-capacity units, so the "better" units are all higher-wattage;  and (b) you DO need a PSU with enough capacity to handle the start-up current in system with a lot of drives.

 

I think the 360w Seasonic is a good choice => they do make a 300w 80+ Bronze unit, but the Bronze certification level is 5% lower efficiency than Gold at 20% load ... so I think you're better off with the 360w unit.

 

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I think I'm leaning toward the first one. 

 

Any of them will work, but as I just noted, I'd go with the 360w unit.

 

Assume your idle power draw is 30 watts -- even lower than I assumed above (I think 35w is more realistic).  That would be a 10% draw on a 300w unit; or a 8.3% draw on a 360w unit.  Both of these are well below the 20% certification level -- so it's reasonable to assume that both units will be operating at 5-10% lower efficiency than they're rated at.    Just for grins, assume the 300w unit is "only" 5% less efficient than it's rated, but the 360w unit is 10% less efficient (NOT at all likely ... if anything, a Gold rated PSU is likely to drop LESS than a Bronze rated unit).

 

If that was, however, the case, note that a 10% drop from 87% (Gold) is exactly the same efficiency as a 5% drop from 82% (Bronze) => so both PSU's would be operating at 77% efficiency.

 

What's MORE likely is that they'd both drop by about the same % efficiency ... which means the 360w Gold certified unit would be 5% more efficient than the 300w unit.

 

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Thanks for helping me on the math Gary.

 

I'll get that 360 and stop fretting about it. 

 

Bonus:  its Haswell certified, affording it a little bit extra "future proofing" (if that even exists).  That plus it being Gold plus it actually being able to fit in my case plus it getting your nod of approval (and that does mean something to me, thanks)... well worth the $26 extra.

 

Done and done.

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The vast majority of our generation is exported to the US already.  Advantage of having GOBS of mountains and runoff.  All of it is "clean" too (we only have hydro powered)... no coal, no gas, etc.  Of course there's a dark side nobody likes to talk about (damming = flooding = a LOT of natural habitat getting displaced), but hey.... its cheap!

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