Dual Power Supply Cases - why? What needs 2 PSUs?

[Zion Halcyon]

Just something I came across, that some enthusiast cases have room for dual PSUs.

My question I guess is why?

Is there an inherent enthusiast benefit to using 2 PSUs? What even supports that?

Totally clueless, so wondering if people more familiar than I with multiple PSU configurations can enlighten me.

 

[Nenu]

Where enough power cannot be drawn from one mains socket.
Where you cant get big enough PSUs.
Where you have enough high power gfx cards to overload a high power PSU.
Where its cost effective to use 2 lower power PSUs instead of one very high power.
...

Any PC can support 2 PSUs.
Whether they will fit is another matter.

 

[Tsumi]

Top tier cards can draw up to 350 watts or more overclocked. That's 1400 watts already for a quad-GPU system. Top end Intel CPUs can pull 250+ watts overclocked. 1650 watts for just the CPUs and GPUs, assuming an extreme system, with the largest quality PSUs being 1600 watts in size.

 

[Zion Halcyon]

I see, so really dual psus are most likely for 3 and 4 card configurationstud.

 

[N4CR]

That or shit-loads of drives or just wanting to do big psu on a budget, or reliability.

Also cost, here they are ~200 USD for anything good in 700W range. I can buy two quality 500W PSUs for about the same price, then not have to care what card(s) in future I use. More $ for ram/gpu/whatever.

Another advantage is more filtering, so slightly smoother power with two anyway, this is good for stability if you're hammering card(s) and cpu. E.g. voltage drop from hammering 300-400W on a single PSU will not drop the other PSU running mobo/CPU. Of course you can do this with one big one but, if you can fit two PSUs, it's only a power efficiency hit. I like to do max effort air cooled builds, so it's nice to have two PSUs and not worry about adding another card. Also out in middle of nowhere, so if a PSU fails I can still work with some re-plugging of things. That's why my business rigs are redundant PSUs but that's controlling lots of equipment in live settings.

Been running a dual sided case since early 00's, will never go back to a single sided case. Airflow reasons alone are worth it. Sure it looks like a big blue Aircon unit on wheels for LANs but IDGAF. Sleeper styles

I want to do a fanless HEDT build next. Dual fanless 500W psus ftw.

 

[Quartz-1]

Top end Intel CPUs can pull 250+ watts overclocked. 1650 watts for just the CPUs and GPUs, assuming an extreme system, with the largest quality PSUs being 1600 watts in size.

Where you cant get big enough PSUs.

Superflower have a PSU that can deliver 2KW, the Leadex Platinum 2000W. As such, there's really no need for a gamer to have more than one PSU, even in a quad GPU dual CPU system. Though I have considerable sympathy for having two or more silent PSUs.

 

[Nenu]

Superflower have a PSU that can deliver 2KW, the Leadex Platinum 2000W. As such, there's really no need for a gamer to have more than one PSU, even in a quad GPU dual CPU system. Though I have considerable sympathy for having two or more silent PSUs.

You serious?
Some areas cant get them and some mains outlets cannot supply that.
And then theres the cost.
Plenty of need.

All stated in my op.

 

[Fractal Design NA]

A friend of mine has a dual PSU system and swears by it, but I'm not sure I'd call it a call it a PC given it also plugs into two 220 volt outlets and needs a pair of 20,000btu AC units to cool. You can never have too much power I guess, but I sure wouldn't want to swap electric bills with the guy.

 

[morningreis]

I was looking into this the other day and came across this very informative post:

The vast majority of people who use two power supplies don't need to, and waste money or endanger their rigs doing so. It's only a valid approach in a very small handful of scenarios, and is otherwise either an unnecessary over-complication, or a dangerous jury rig solution.

The main thing people do wrong with dual power supplies is to think they even need it. They look at a GTX580, then look at power consumption charts and think "OMG 500W OMG OMG NEED MOAR POWER" when in fact that's the total system power consumption; the card itself only pulls ~300W. So then they decide to supplement their already more-than-sufficient 650-850W PSU with another PSU, wasting money and making life more difficult, what with having to stash another PSU somewhere inside their case and hiding a bunch more cables.

The next worse thing people do is do dual PSUs with cheap units. Most power supplies under $100, and all under $50, use a technology called "group regulation" to reduce costs. There's a bunch of technical stuff I could throw at you; but the gist of it is that the current on the +12V and +5V rails on a group regulated power supply must stay within a certain approximate ratio to one another (say 3A of +12V for every 1A of +5V, +/-20%) or else the voltage regulation will go out of whack. +12V load too low? +5V voltage drops and +12V voltage soars. +5V load too low? +5V soars and +12V drops.

The secondary PSU in a dual-PSU usually has no +5V load at all, or at most 1-2A, meaning that the +12V voltage will droop significantly; on high-end group regulated units it will fall to 11.6-11.7V, which is in-spec but poor. On low-end group regulated units +12V might drop to 11.3-11.5V, out of spec or almost. Out of spec voltage (>11.4V) can cause component malfunction; bluescreens and random shut downs, and will prevent many hard drives from functioning at all.. Very low, but in-spec voltage (11.4-11.6V) can cause poor overclocking results, occasional instability, excessive wear on component power circuitry, and can cause hard drive issues over time.

Dual PSUs should only be used when both power supplies are high quality and use independent regulation, or even better "DC-DC" regulation. It's only a useful approach when dealing with systems that pull >1000W; then two quality 650W+ indy/DC-DC regulated units may be used in place of a single 1000W+ unit. Even then you may run into issues of crosstalk leading to greater effective ripple on power regulated devices (motherboard, graphics card, RAID controllers), and units that rely on +12V v-sense may suffer poor voltage regulation if the cable with their v-sense wires is not in use.

In short, don't do it unless you really have to (2+ graphics cards, 2+ processors,...) and if you do, pick high quality PSUs. Although even with a single PSU, it is the only component connected to and with the potential to fry literally everything else. I wouldn't ever chance a PSU that wasn't top quality - dual or single.

 

[Dead Parrot]

Two power supplies can allow for redundancy if up time is really important. This does require some planning as it does little good to have dual PS plugged into the same circuit. One janitor with vacuum or person with hair dryer can still take the system down. Dual UPS help but both PS and UPS each have to be large enough to support the load with a bit of extra just in case. Unless you get really extreme, there is still a single point of failure at the building mains.

 

[thebeephaha]

I had a server build where I was using about 20 drives. At the time (like 10 years ago when most PSUs were still quite inefficient and not very powerful) I wired up a second PSU to be able to power the system up properly as my storage controller didn't support staggered spin up of the drives. The massive load at boot with a single PSU was just too much and it was a gamble if it would turn on without shutting down from overload, and if it did turn on and stay on, sometimes not all the drives would initialize. I think now days with the massively efficient and powerful PSUs out there the need for two PSUs aside from redundancy is very low.

 

[Quartz-1]

Unless you get really extreme, there is still a single point of failure at the building mains.

In such cases the UPS is there to provide power long enough for the generator to be started. BTDTGTTS. It seems odd plugging all the PSUs into the same UPS or circuit, but there's a method behind it.