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why don't power supplies come with a built in UPS?

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  • SteveRichter

    just lost power for a split second, which caused the PC to reboot ...

    Are there power supplies which enable a PC to withstand such a brief power hit? I normally build my PC from parts and I don't skimp on the power supply. Yet, I have never noticed any being sold with a built in UPS or advertised with the ability to maintain power for a few seconds.

    I have a small IBM AS400 server running sometimes. And more often than not when I lose power like this the AS400 stays up while the PC falls flat.

     

  • evildictait​or

    I suspect it's mainly because mains power is usually uninterrupted and UPSes are expensive and unwieldy , and therefore not suitable for normal customers making default PC purchases.

    If your mains power is routinely cutting out, there's nothing to stop you buying your own UPS for your machine.

  • kettch

    @evildictaitor: Also, a UPS provides power conditioning that a surge suppressor can't. So, you'll be protected from a wide range of power abnormalities.

  • BitFlipper

    A good solution might be to use a super capacitor in a PSU to give you enough power to last some amount of seconds (a few minutes would be great, then you can power off gracefully). But are enough people going to want to pay extra for this feature to make it viable?

    Last time I looked into this, super capacitors had roughly 1/10 the energy density of a similarly sized battery. If you are really interested you can probably calculate what physical size it needs to be to get some amount of uptime based on the size of existing UPS system batteries.

  • figuerres

    , SteveRichter wrote

    just lost power for a split second, which caused the PC to reboot ...

    Are there power supplies which enable a PC to withstand such a brief power hit? I normally build my PC from parts and I don't skimp on the power supply. Yet, I have never noticed any being sold with a built in UPS or advertised with the ability to maintain power for a few seconds.

    I have a small IBM AS400 server running sometimes. And more often than not when I lose power like this the AS400 stays up while the PC falls flat.

     

    well here are some things to take into account:

    1) added cost

    2) added weight

    3) the battery is toxic lead /acid in most of them

    4) UPS and other shippers have to be notified and the battery must be not connected in shipping.

    5) if you want more runtime then ???

    6) added size to the pc

    for the pc Mfg how do they gain by adding that part  given the added costs and possible shipping and other issues?  how many buyers would want this ?

    the AS400 may be built different than a desktop system, IBM has a lot invested in highly reliable gear for businesses.

     

  • SteveRichter

    , kettch wrote

    @evildictaitor: Also, a UPS provides power conditioning that a surge suppressor can't. So, you'll be protected from a wide range of power abnormalities.

    and I guess a UPS has a minimum size that would make a power supply with a built in UPS too big?  I don't have a particular problem with power, with is why I dont have a UPS.

    I find it interesting that the economics of mass production seems to make the production of products out of the ordinary much more expensive by comparison. Which limits there availabilty

  • kettch

    @SteveRichter: Actually there is a minimum size. The UPS switching and conditioning hardware is roughly the same size as the battery. If you take a look at even a small size UPS the batter is only aabout 1/3 or the total volume.

    The extra effort of having a UPS goes far beyond just causing your computer to shut down when the power drops. There are all sorts of transient events that can not only cause reboots, but also damage to components. IMO it's just not worth the risk.

  • Blue Ink

    @SteveRichter: if all you want is your PC to survive a power glitch in the split second range, you could theoretically just use a simple circuit that adds large capacitors on the low voltage lines of your PSU; the problem is that handling the "Power Good" line properly may not be straightforward.

    My advice: get a laptop.

  • SteveRichter

    , Blue Ink wrote

    My advice: get a laptop.

    exactly. If it is doable to put a battery in a laptop, why not have an option to put a small battery in a desktop. I would pay for that.  ( figuerres, there are not problems shipping laptops with connected batteries. )

    btw, I lost power last week and today. IE both times lost stuff. Where I lost my IE most popular sites, had to reenter passwords.

     

  • androidi

    @SteveRichter:

    I'd be happy if the standard ATX supplies would have a way of communicating that "oops, main power disconnected, you have about 0-5 seconds to flush data to disk depending on how much juice there is in my capacitors).

    Technically it could be made such that it

    1) sends a message that mains power is out

    2) after certain standardized amount of milliseconds, 12v output is cut, this gives enough time to spinning HDD to decide to say "OK main power cut and no time to write more data to disk, I'm going to try to send this data in my cache back to the OS which can then send it to a 3 or 5 volt flash memory device for store until such time power is restored

    3) there could be motherboard input for a battery that is used to keep RAM powered after the PSU caps run out and there was not enough time to flush data to SSD. maybe a driver could be made to write the cpu and RAM to SSD with this battery power at minimal CPU clock speed while GPU's etc buses are powered off

    4) apps could request, with user approval, access to the "mains power cut" message, so if user wanted the data of a particularly important app saved with priority over other apps, that could be done.

  • figuerres

    , SteveRichter wrote

    *snip*

    exactly. If it is doable to put a battery in a laptop, why not have an option to put a small battery in a desktop. I would pay for that.  ( figuerres, there are not problems shipping laptops with connected batteries. )

    btw, I lost power last week and today. IE both times lost stuff. Where I lost my IE most popular sites, had to reenter passwords.

     

    not my rules, talk to the shipping folks ...  also moving companies have that rule.

    I do not know if Li-ION is any safer than the UPS type batteries and I do wonder if they might start using Li type in a ups or if for some reason the old kind are better for a UPS ??

     

  • androidi

    @SteveRichter:

    Also I would say that in most scenarios apps can be programmed to save some essential state every now and then, so if IE is losing data written in forms while power goes out or when you accidentally press escape or mouse back button, I think that problem can be solved by the IE team, but if the OS doesn't get a message in time to flush the data to disk when the power cuts, then you lose data.

    In addition I would like if the motherboard included some basic power monitoring of the various PSU rails to see if the PSU capacitors are going dry or there is some other power quality issue as this could be exposed in a system similar to HDD's "SMART" where user could then get a message that the PSU is about to die.

    One way to implement this is for the OS to monitor the PSU rails at high frequency during a short test run now and then, essentially creating a statistical profile of how the rails act when loaded. Of course the load profiling would need to be done in a way that stays valid over time, this could be done by the profiling service telling all buses to go to power saving state, and then use the CPU to perform some intensive operation to see how the PSU voltages act. If they start acting differently it could signal poorer performance in capacitors somewhere (mainboard or PSU).

  • figuerres

    , androidi wrote

    @SteveRichter:

    I'd be happy if the standard ATX supplies would have a way of communicating that "oops, main power disconnected, you have about 0-5 seconds to flush data to disk depending on how much juice there is in my capacitors).

    Technically it could be made such that it

    1) sends a message that mains power is out

    2) after certain standardized amount of milliseconds, 12v output is cut, this gives enough time to spinning HDD to decide to say "OK main power cut and no time to write more data to disk, I'm going to try to send this data in my cache back to the OS which can then send it to a 3 or 5 volt flash memory device for store until such time power is restored

    3) there could be motherboard input for a battery that is used to keep RAM powered after the PSU caps run out and there was not enough time to flush data to SSD. maybe a driver could be made to write the cpu and RAM to SSD with this battery power at minimal CPU clock speed while GPU's etc buses are powered off

    4) apps could request, with user approval, access to the "mains power cut" message, so if user wanted the data of a particularly important app saved with priority over other apps, that could be done.

     

    part of that is already in place...  when windows is shutting down it sends a general message to all running apps that it is going to halt and they need to shut down. each app is then supposed to do what they need to do.

    and the UPS power service in windows is there to listen to messages about power state and to start a shutdown when it gets the right message.

    so I guess if the psu had a few more parts and a data line to chat with windows ....

  • kettch

    I'm still not seeing how any of this is (1) cheaper and easier for the user, or (2) simpler.

  • elmer

    I guess that the majority of new computers *DO* come with a UPS, as the majority of PCs now sold are either laptops or tablets.

    However, all of our HP servers have a small L-Ion battery on the disk controller, to retain unwritten data in the event of a power-out, despite the fact that the entire server room is on a UPS (you can never be too sure) and it should not be hard to include that in a PC's M/Board design, using a small button-sized battery.

    Nevertheless, a good quality PS should be able to withstand momentary interruptions to the supply, as most quality PS's have at least a limited capacitance, but there are no hard & fast rules that allow you to spot the 'quality' of the PS in a PC - it tends to be hit & miss (so to speak).

    At the end of the day, for protecting running applications, there is no substitute for a decent UPS, and we have them scattered about our offices, for all desktops and terminals - sometimes with multiple devices on the one UPS - because the supply in our area is notoriously unreliable, in outage, voltage and spikes.

  • Blue Ink

    , SteveRichter wrote

    *snip*

    exactly. If it is doable to put a battery in a laptop, why not have an option to put a small battery in a desktop. I would pay for that.  ( figuerres, there are not problems shipping laptops with connected batteries. )

    btw, I lost power last week and today. IE both times lost stuff. Where I lost my IE most popular sites, had to reenter passwords.

    It is doable; it's only expensive. If widely adopted it could be less expensive than an external UPS (and more efficient), but for most people black-outs are infrequent enough that it wouldn't make sense to pay more for their desktops.

    If you are into DIY electronics, it's not very difficult to make it yourself; again, it's just expensive.

  • elmer

    Internal UPS's have been done in the past, but they tend to be quite bulky and (relatively) expensive.

    E.g. http://www.beam-tech.com/093001/prd_pgs/internal_ups.htm 

  • cheong

    It's because a UPS normally last longer than a power supply.

    I live in some dusty area and the power supplys of computers at home usually last no longer than a year even when I regularly remove dust from it. A normal UPS can last for 3-5 years if you care to replace the acid inside every 6-9 months.

    And note that the process of "replacing acid" can damage the power supply easily if you're not careful. Common rechargable batteries are good but expensive. I remember that the battery of my IBM notebook cost around HKD 1000 each.

    Also, even the "entry level" UPS can serve up to 2 machines at the same time. It's more convenient to build them as seperate parts.

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