Single-rail vs. multi-rail power supplies?

Discussion in 'Processors' started by Yousuf Khan, Mar 21, 2012.

  1. Yousuf Khan

    Yousuf Khan Guest

    I currently have a desktop with a Zalman 600W PS, it was a pretty nice
    PS a few years ago when I got it, but now it looks like the system has
    been upgraded and grown again, and I'm starting to see signs that it's
    not producing enough power for the components anymore. So I'm looking at
    the market for bigger PS's, likely 750W+.

    When I got the Zalman, multi-rail +12V were the de riguer feature of the
    day. Now that I'm shopping for them again, I see that the manufacturers
    have done an about-face, and they are advertising the advantages of
    single-rail +12V. The old 600W had 4 rails at 16 Amps each. The new
    single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!
    Why have the manufacturers done the about-face on single-rail vs.
    multi-rail?

    Yousuf Khan
     
    Yousuf Khan, Mar 21, 2012
    #1
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  2. Yousuf Khan

    Paul Guest

    Yousuf Khan wrote:
    > I currently have a desktop with a Zalman 600W PS, it was a pretty nice
    > PS a few years ago when I got it, but now it looks like the system has
    > been upgraded and grown again, and I'm starting to see signs that it's
    > not producing enough power for the components anymore. So I'm looking at
    > the market for bigger PS's, likely 750W+.
    >
    > When I got the Zalman, multi-rail +12V were the de riguer feature of the
    > day. Now that I'm shopping for them again, I see that the manufacturers
    > have done an about-face, and they are advertising the advantages of
    > single-rail +12V. The old 600W had 4 rails at 16 Amps each. The new
    > single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!
    > Why have the manufacturers done the about-face on single-rail vs.
    > multi-rail?
    >
    > Yousuf Khan


    That's a good question.

    The terminology is adjusted, to whatever sells power supplies.
    That's a rule of thumb about marketing. You don't actually
    have to be honest about what you're selling. You describe it
    in any way, that will make you successful. if a competitor
    touted single rail output, and he's selling supplies,
    then you chime in with a matching story.

    These are some examples of power supply designs.

    AC ---- switcher --- 65A ---- 75A_limiter ----+---- 12V1
    |
    +---- 12V2
    |
    +---- 12V3

    OK, let's take a Molex, and short +12V to ground on that one.
    The whole yellow and black wires on the Molex, start to glow,
    the plastic melts off the wire, and so on. While this is a
    "true single rail" design, notice it's a safety hazard. The
    design could provide around 12*75 = 900W of thermal energy,
    if you adjusted the loading just right. If the short had a
    resistance of 0.2 ohms, the supply likely wouldn't shut off.
    A dead short, might trip it OK. Hard to guess...

    Now, let's make a design closer to the intentions of the
    IEC60950 spec, and limit individual outputs to a safer level.
    This still isn't compliant, but its closer to the spirit
    of the limitations you're supposed to apply to secondary outputs.

    AC ---- switcher ----- 65A ---+-- 25A_limiter --------- 12V1
    |
    +-- 25A_limiter --------- 12V2
    |
    +-- 25A_limiter --------- 12V3

    Now, the wires may still get hot, the connectors burn, but
    the amount of power in any individual circuit, cannot exceed
    12*25 = 300W. The limiter works, by switching off the supply,
    if the current flow level is exceeded. An overload in any
    branch, can switch it off.

    Power supplies built as follows, are "true independent output"
    circuits. A hint you're getting the real McCoy, is the chassis
    is 1" to 1.5" longer than the competing power supply of the
    same capacity. The density cannot be as great, because of
    the replicated circuits. I don't think that many, were
    actually built this way. If you open your Zalman, it probably
    doesn't match this topology. Your Zalman, might be the
    previous figure.

    AC -- DC ---+-- switcher ----- 22A ------ 25A_limiter --- 12V1
    300V |
    +-- switcher ----- 22A ------ 25A_limiter --- 12V2
    |
    +-- switcher ----- 22A ------ 25A_limiter --- 12V2

    I'd say that middle design, looks pretty good. No matter
    whether my marketing department describes it as "one rail"
    or "multi rail". The size of the supply, or the lack of
    replicated circuits inside, can help you judge the
    true topology.

    I don't own a copy of IEC60950, so I can't copy/paste
    the appropriate part. And the last time I looked, I couldn't
    find a copy "floating" on the web. The keyword "SELV" comes
    to mind, but that's about all I remember now.

    HTH,
    Paul
     
    Paul, Mar 21, 2012
    #2
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  3. Yousuf Khan

    Rod Speed Guest

    Yousuf Khan wrote

    > I currently have a desktop with a Zalman 600W PS, it was a pretty nice PS a few years ago when I got it, but now it
    > looks like the system has been upgraded and grown again, and I'm starting to see signs that it's not producing enough
    > power for the components anymore.


    What signs are those exactly ?

    That wouldnt normally be the case unless you have one hell of a video card in it.

    > So I'm looking at the market for bigger PS's, likely 750W+.


    > When I got the Zalman, multi-rail +12V were the de riguer feature of the day. Now that I'm shopping for them again, I
    > see that the
    > manufacturers have done an about-face, and they are advertising the
    > advantages of single-rail +12V. The old 600W had 4 rails at 16 Amps each.


    And I would be amazed if you are exceeding that.

    > The new single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!


    And even the biggest is only 1A more than you currently have.

    > Why have the manufacturers done the about-face on single-rail vs. multi-rail?


    So they dont have to have 4 separate 12V regulators.
     
    Rod Speed, Mar 21, 2012
    #3
  4. Yousuf Khan

    Rob Guest

    On 22/03/2012 8:52 AM, Yousuf Khan wrote:
    > I currently have a desktop with a Zalman 600W PS, it was a pretty nice
    > PS a few years ago when I got it, but now it looks like the system has
    > been upgraded and grown again, and I'm starting to see signs that it's
    > not producing enough power for the components anymore. So I'm looking at
    > the market for bigger PS's, likely 750W+.
    >
    > When I got the Zalman, multi-rail +12V were the de riguer feature of the
    > day. Now that I'm shopping for them again, I see that the manufacturers
    > have done an about-face, and they are advertising the advantages of
    > single-rail +12V. The old 600W had 4 rails at 16 Amps each. The new
    > single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!
    > Why have the manufacturers done the about-face on single-rail vs.
    > multi-rail?
    >
    > Yousuf Khan



    Well get yourself one that has good weight and a three year warranty.

    Bigger is not necessarily any better and depends on your PC configuration.
     
    Rob, Mar 21, 2012
    #4
  5. Yousuf Khan

    Yousuf Khan Guest

    On 21/03/2012 6:34 PM, Rod Speed wrote:
    > Yousuf Khan wrote
    >
    >> I currently have a desktop with a Zalman 600W PS, it was a pretty nice PS a few years ago when I got it, but now it
    >> looks like the system has been upgraded and grown again, and I'm starting to see signs that it's not producing enough
    >> power for the components anymore.

    >
    > What signs are those exactly ?


    Well, we've discussed those on csiphs already, mainly the optical drives
    sending controller error messages even when they are not being used, and
    I'm also noticing some occasional spin retry errors on a few of my
    internal HDD's.

    > That wouldnt normally be the case unless you have one hell of a video card in it.


    Well, the video card is not a monster of any kind, it's more upper
    mainstream, an AMD Radeon 6870.

    >> So I'm looking at the market for bigger PS's, likely 750W+.

    >
    >> When I got the Zalman, multi-rail +12V were the de riguer feature of the day. Now that I'm shopping for them again, I
    >> see that the
    >> manufacturers have done an about-face, and they are advertising the
    >> advantages of single-rail +12V. The old 600W had 4 rails at 16 Amps each.

    >
    > And I would be amazed if you are exceeding that.


    Well, I ran my system components through a few power supply calculators:

    http://extreme.outervision.com/PSUEngine said I needed 580W.
    http://www.thermaltake.outervision.com/Power said I needed 574W.
    http://support.asus.com/powersupply.aspx said I needed 900W!!!

    Obviously, the Asus rating is an outlier so I'm ignoring that one, but
    the other two seem to agree pretty close to each other, and that level
    is pretty close to the maximum power rating (within 96-97%) of my old
    PS. And with the age of the PS advancing in years, its maximum capacity
    might actually be decreasing over time.

    When I first obtained this 600W PS, the PS calculator showed that my
    system requirement was only in the upper 400W range. So I thought I had
    more than enough leeway, but it looks like the various upgrades have
    quickly taken up most of that leeway since then.

    >> The new single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!

    >
    > And even the biggest is only 1A more than you currently have.


    When you add it up, yes the 4 separate rails come out to about 64A, but
    the point is is it possible that some of the rails are overloaded by
    themselves? Would it be easier to distribute the power if there was a
    single larger rail rather than 4 smaller rails?

    >> Why have the manufacturers done the about-face on single-rail vs. multi-rail?

    >
    > So they dont have to have 4 separate 12V regulators.


    I found one possible explanation here:

    http://www.overclock.net/t/88626/info-do-you-need-multiple-12v-rails

    According to the above, the EU had mandated that no single +12V rail
    could exceed 20A, and that later Intel also embraced that EU rule, and
    further reduced that down to 18A. But now it looks like Intel no longer
    requires the 18A rule. I'm not sure if the EU has also dropped its 20A
    requirement, but here in North America there is no longer a need to have
    separate rails anymore, so we can go to single super-rails.

    Yousuf Khan
     
    Yousuf Khan, Mar 21, 2012
    #5
  6. Yousuf Khan

    Paul Guest

    Yousuf Khan wrote:

    >
    > Well, I ran my system components through a few power supply calculators:
    >
    > http://extreme.outervision.com/PSUEngine said I needed 580W.
    > http://www.thermaltake.outervision.com/Power said I needed 574W.
    > http://support.asus.com/powersupply.aspx said I needed 900W!!!
    >
    > Obviously, the Asus rating is an outlier so I'm ignoring that one, but
    > the other two seem to agree pretty close to each other, and that level
    > is pretty close to the maximum power rating (within 96-97%) of my old
    > PS. And with the age of the PS advancing in years, its maximum capacity
    > might actually be decreasing over time.
    >
    > When I first obtained this 600W PS, the PS calculator showed that my
    > system requirement was only in the upper 400W range. So I thought I had
    > more than enough leeway, but it looks like the various upgrades have
    > quickly taken up most of that leeway since then.


    The HD6870 is 124 to 147 watts. One of the cards quoted here could be
    an overclock. Try doing your power calculation manually.

    http://www.xbitlabs.com/articles/graphics/display/asus-eah6870-directcu_4.html#sect0

    Paul
     
    Paul, Mar 22, 2012
    #6
  7. Yousuf Khan

    KR Guest

    On Mar 22, 7:52 am, Yousuf Khan <> wrote:
    > I currently have a desktop with a Zalman 600W PS, it was a pretty nice
    > PS a few years ago when I got it, but now it looks like the system has
    > been upgraded and grown again, and I'm starting to see signs that it's
    > not producing enough power for the components anymore. So I'm looking at
    > the market for bigger PS's, likely 750W+.
    >
    > When I got the Zalman, multi-rail +12V were the de riguer feature of the
    > day. Now that I'm shopping for them again, I see that the manufacturers
    > have done an about-face, and they are advertising the advantages of
    > single-rail +12V. The old 600W had 4 rails at 16 Amps each. The new
    > single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!
    > Why have the manufacturers done the about-face on single-rail vs.
    > multi-rail?
    >
    >         Yousuf Khan




    Traditionally it was always considered good practice to separate the
    power for
    digital and analog circuits as much as possible to prevent
    interference.
    This would especially be the case in audio systems.

    In the case of a PC, this would mean keeping the supply for motors
    (such as
    Hard Drives, CD ROMS etc on a separate circuit, so as to minimise any
    electrical
    noise from these from interfering with digital circuits - assuming
    this really is a problem in a modern PC.

    Usually having separate supply cables from a common power source is
    sufficient.



    I would suggest it is more likely done to keep the currents manageable
    on particular circuits however.
    You might have 60A available, but in cases like this where one circuit
    is never going to need more than (say) 15a,
    it is safer to split it into 4 separate circuits.

    Exactly the same is done in your home fusebox in having separate fuses
    and circuits for your lights, power points,
    air con, water heater, stove etc, rather than just having a single
    200A fuse for the entire lot.
     
    KR, Mar 22, 2012
    #7
  8. Yousuf Khan

    Rod Speed Guest

    Yousuf Khan wrote
    > Rod Speed wrote
    >> Yousuf Khan wrote


    >>> I currently have a desktop with a Zalman 600W PS, it was a pretty
    >>> nice PS a few years ago when I got it, but now it looks like the
    >>> system has been upgraded and grown again, and I'm starting to see
    >>> signs that it's not producing enough power for the components anymore.


    >> What signs are those exactly ?


    > Well, we've discussed those on csiphs already, mainly the optical drives sending controller error messages even when
    > they are not being used,


    OK, I dont believe that those would be because you
    are exceeding the 600W rating of the power supply.

    I meant that the power supply may be failing, putting more noise
    on the rails than is allowed. If thats the case, just replacing it with
    another copy of the 600W supply should see that problem go away.

    > and I'm also noticing some occasional spin retry errors on a few of my internal HDD's.


    Thats unlikely to be because doesnt have enough current on the
    12V rail even tho you do have quite a few hard drives from memory.

    If that is the problem, it makes more sense ot replace some
    of the smaller drives with new much larger ones than it does
    to change the power supply, tho you should change the power
    supply because of the optical drive symptoms you are getting
    to see if thats due to the power supply.

    You dont necessarily need such a big supply for that test tho.

    >> That wouldnt normally be the case unless you have one hell of a video card in it.


    > Well, the video card is not a monster of any kind, it's more upper mainstream, an AMD Radeon 6870.


    Yeah, it only need 2 75W power connectors.

    The 12V rails on that power supply are way above what it needs.

    >>> So I'm looking at the market for bigger PS's, likely 750W+.


    >>> When I got the Zalman, multi-rail +12V were the de riguer feature
    >>> of the day. Now that I'm shopping for them again, I see that the
    >>> manufacturers have done an about-face, and they are advertising the
    >>> advantages of single-rail +12V. The old 600W had 4 rails at 16 Amps each.


    >> And I would be amazed if you are exceeding that.


    > Well, I ran my system components through a few power supply calculators:


    I dont buy those. What matters is AMD's statement of what the video card needs,
    http://www.amd.com/us/products/desk...6870/pages/amd-radeon-hd-6870-overview.aspx#3
    and thats where that 2 75W power connectors comes from,
    and that detail you have already provided on 4 12V 16A rails.

    Those are 192W rails, each one of them.

    > http://extreme.outervision.com/PSUEngine said I needed 580W.
    > http://www.thermaltake.outervision.com/Power said I needed 574W.
    > http://support.asus.com/powersupply.aspx said I needed 900W!!!


    Yeah, thats obviously silly.

    > Obviously, the Asus rating is an outlier so I'm ignoring that one, but the other two seem to agree pretty close to
    > each other,


    But nothing like what you get when you calculate the 12V rails explicitly.

    That power supply handles the video card fine with 2 of the rails
    and you have two more for your hard drives which wont take
    anything like 384W even if they are all trying to spin up at once.

    > and that level is pretty close to the maximum power rating (within 96-97%) of my old PS.


    Thats the problem with those power supply 'calculators', they
    dont actually calculate what matters, the 12V rail currents.

    And the 900W supply you are considering only has 1A more
    12V current available anyway.

    > And with the age of the PS advancing in years, its maximum
    > capacity might actually be decreasing over time.


    Nope, that doesnt happen.

    What you can get is a deterioration of the low ESR caps and that
    sees a lot more noise on the rails than there should be, but you dont
    see a reduction in the rail current capacity and even if you did you
    are nowhere near the maximum currents on any of those 12V rails.

    > When I first obtained this 600W PS, the PS calculator showed that my system requirement was only in the upper 400W
    > range.


    Do you mean that the calculator has changed, or that
    what you have in that system has changed that much ?

    > So I thought I had more than enough leeway, but it looks like the various upgrades have quickly taken up most of that
    > leeway since then.


    Or the calculator has changed since then. What have you changed upgrade wise ?

    >>> The new single rails I'm seeing seem to have a rail at anywhere from 45A to 65A!


    >> And even the biggest is only 1A more than you currently have.


    > When you add it up, yes the 4 separate rails come out to about 64A, but the point is is it possible that some of the
    > rails are overloaded by themselves?


    Nope, not with that particular video card.

    > Would it be easier to distribute the power if there
    > was a single larger rail rather than 4 smaller rails?


    No, in fact its harder because you cant do a remote sense
    so that the highest current rail is seeing 12V at the pins
    without increasing what the other connects get at the pins.

    Not that that matter much, the specs on the variation in the 12V rails is pretty wide.

    And you have the other problem with a single rail too, limiting the
    current to say 75A can still see a decent fire with some shorts.

    You dont get that with 4 seperate 16A max current rails. 200W
    isnt that bad as long as there is someone around to turn it off.

    800W can be pretty spectacular in the very small space of a
    single molex nylon connector.

    >>> Why have the manufacturers done the about-face on single-rail vs. multi-rail?


    >> So they dont have to have 4 separate 12V regulators.


    > I found one possible explanation here:


    > http://www.overclock.net/t/88626/info-do-you-need-multiple-12v-rails


    > According to the above, the EU had mandated that no single +12V rail could exceed 20A, and that later Intel also
    > embraced that EU rule, and further reduced that down to 18A. But now it looks like Intel no longer requires the 18A
    > rule.


    Yeah, if thats accurate, it likely is the reason for the change.

    > I'm not sure if the EU has also dropped its 20A requirement, but here in North America there is no longer a need to
    > have separate rails anymore, so we can go to single super-rails.


    I dont like the idea of a single rail that can in theory deliver 800W
    being able to do short circuit protection adequately myself.

    Corse most of the time a short would just blow off quite literally but that doesnt always happen.
     
    Rod Speed, Mar 22, 2012
    #8
  9. Yousuf Khan

    Yousuf Khan Guest

    Yousuf Khan, Mar 22, 2012
    #9
  10. Yousuf Khan

    Yousuf Khan Guest

    On 21/03/2012 11:51 PM, Rod Speed wrote:
    > Yousuf Khan wrote
    >> Well, we've discussed those on csiphs already, mainly the optical drives sending controller error messages even when
    >> they are not being used,

    >
    > OK, I dont believe that those would be because you
    > are exceeding the 600W rating of the power supply.


    Maybe not the overall power supply rating, but maybe some of the
    individual rails might be undercharged.

    > I meant that the power supply may be failing, putting more noise
    > on the rails than is allowed. If thats the case, just replacing it with
    > another copy of the 600W supply should see that problem go away.
    >
    >> and I'm also noticing some occasional spin retry errors on a few of my internal HDD's.

    >
    > Thats unlikely to be because doesnt have enough current on the
    > 12V rail even tho you do have quite a few hard drives from memory.


    Well, I do have six internal hard drives right now, and one optical
    drive (Blu-Ray burner). It's the number of error messages that I'm
    seeing on the BR burner that's got me most worried, but also recently I
    saw a worrying pop-up message from Hard Disk Sentinel that it is
    predicting an imminent failure of my boot drive too. I don't know which
    of the rails all of these drives are connected to, but if they are all
    connected to the same rail (very likely) then they might be all sharing
    current from a diminished resource. I wonder how much current each of
    the optical and hard drives use?

    >>> That wouldnt normally be the case unless you have one hell of a video card in it.

    >
    >> Well, the video card is not a monster of any kind, it's more upper mainstream, an AMD Radeon 6870.

    >
    > Yeah, it only need 2 75W power connectors.
    >
    > The 12V rails on that power supply are way above what it needs.


    One or two rails would go to the motherboard, another one would go to
    the video card, and the last rail would be left for all of the rest of
    the peripherals. I've mostly had no problems with motherboard components
    (CPU, RAM, PCI cards), no problems with the video card, but the rest of
    the system is all supplied by one rail, such as drives and fans and
    lights. I won't really notice any power problems with the fans or
    lights, but the drives might be pretty sensitive.

    > That power supply handles the video card fine with 2 of the rails
    > and you have two more for your hard drives which wont take
    > anything like 384W even if they are all trying to spin up at once.


    I don't think the video card gets two whole rails to itself. The
    motherboard 24-pin connector is one rail which would power the PCI/PCI-e
    slots, chipset and RAM; and maybe it'll feed a few Watts to the CPU too.
    Then another 6-pin plug would be a rail for the CPU alone, which also
    plugs into the motherboard. Then a couple of video power connectors
    would go into the video card, which would likely come from one rail by
    itself. The video card would also receive some power from the
    motherboard through the PCI-e slot. So the video card might have at most
    maybe 1.5 rails for its use (partial motherboard rail & full video
    rail). And the last rail for everything else in the system.

    >> and that level is pretty close to the maximum power rating (within 96-97%) of my old PS.

    >
    > Thats the problem with those power supply 'calculators', they
    > dont actually calculate what matters, the 12V rail currents.
    >
    > And the 900W supply you are considering only has 1A more
    > 12V current available anyway.


    Well, I'm not really considering a 900W PS, more likely a 750W one.

    >> When I first obtained this 600W PS, the PS calculator showed that my system requirement was only in the upper 400W
    >> range.

    >
    > Do you mean that the calculator has changed, or that
    > what you have in that system has changed that much ?


    Yup, the stuff in the system has changed that much. This system is in a
    constant state of evolution, including the case itself. I upgraded from
    a mid-tower with a capacity for only four 3.5" drives to one with six
    3.5" drives, and then it quickly evolved to to fill up those additional
    drive slots. Also there was a video card upgrade, and a CPU upgrade
    along the way too.

    >> When you add it up, yes the 4 separate rails come out to about 64A, but the point is is it possible that some of the
    >> rails are overloaded by themselves?

    >
    > Nope, not with that particular video card.


    I don't think the video card is the issue here at all! Just those drives
    in combination with all of the other powered peripherals inside that
    system. I played around with the figures in one of the PS calculators,
    and I found out that it's assuming 13W per 7200-rpm SATA hard drive, 24W
    per 7200-rpm IDE HDD, 29W per Blu-Ray burner, 34W per DVD burner.

    Based on that I currently have 129W in internal drives alone (4 SATA
    HDD, 2 IDE HDD, 1 BR). When I previously had the dual DVD burners rather
    than the single Blu-Ray, I had 168W worth of drives! This is now
    starting to explain why my two DVD burners failed simultaneously.

    I also have 4x 250mm case fans on the system (they came with the new
    case). Each is regular fan is rated at 12W, and each LED fan is 13W.
    Based on that I have 49W worth of fans (3 regular, 1 LED). Adding to the
    previous figures of 129W and 168W brings them to overall totals of 178W
    and 217W, respectively! If I only have 192W to play with per rail, then
    I was well over when I had two DVD burners, and I'm sitting on the edge
    still now.

    >> Would it be easier to distribute the power if there
    >> was a single larger rail rather than 4 smaller rails?

    >
    > No, in fact its harder because you cant do a remote sense
    > so that the highest current rail is seeing 12V at the pins
    > without increasing what the other connects get at the pins.
    >
    > Not that that matter much, the specs on the variation in the 12V rails is pretty wide.
    >
    > And you have the other problem with a single rail too, limiting the
    > current to say 75A can still see a decent fire with some shorts.


    That is obviously a worry, and that's why they didn't do this in the
    past. I'm hoping that now that they are doing it, that they may have
    found a way to keep it under control these days?

    Yousuf Khan
     
    Yousuf Khan, Mar 22, 2012
    #10
  11. Yousuf Khan

    Rod Speed Guest

    Yousuf Khan wrote
    > Paul wrote


    >> The HD6870 is 124 to 147 watts. One of the cards quoted here could be an overclock. Try doing your power calculation
    >> manually.


    >> http://www.xbitlabs.com/articles/graphics/display/asus-eah6870-directcu_4.html#sect0

    >
    > No, mine is a Sapphire 6870, which might be pretty close to a reference design.


    Most Sapphires arent, actually.

    Its all completely academic, you know that video card works fine on that particular power supply.

    Even if it is loading down one of the 12V rails too much,
    that wont be the rail that used for the optical drives.
     
    Rod Speed, Mar 22, 2012
    #11
  12. Yousuf Khan

    Rod Speed Guest

    Yousuf Khan wrote
    > Rod Speed wrote
    >> Yousuf Khan wrote


    >>> Well, we've discussed those on csiphs already, mainly the optical drives sending controller error messages even when
    >>> they are not being used,


    >> OK, I dont believe that those would be because you
    >> are exceeding the 600W rating of the power supply.


    > Maybe not the overall power supply rating, but maybe some of the individual rails might be undercharged.


    You mean overloaded.

    No, that isnt possible. The video card needs 2 75W supplys.

    Even if they are both supplied from a single 12V rail in that supply,
    thats only 150W from a rail that can deliver 192W, so there is bags
    of margin in hand and you know the video card works fine anyway.

    You cant possibly be exceeding what the other rails can deliver,
    even 10 hard drives wouldnt do that if they are all starting at once,
    and the symptoms you see arent when the drives are starting up
    anyway with the optical drive symptoms.

    >> I meant that the power supply may be failing, putting more noise
    >> on the rails than is allowed. If thats the case, just replacing it with another copy of the 600W supply should see
    >> that problem go away.


    >>> and I'm also noticing some occasional spin retry errors on a few of
    >>> my internal HDD's.


    >> Thats unlikely to be because doesnt have enough current on the
    >> 12V rail even tho you do have quite a few hard drives from memory.


    > Well, I do have six internal hard drives right now, and one optical drive (Blu-Ray burner).


    Thats fine even if they are all on a single 192W 16A rail.

    And you dont see the optical drive symptom at hard drive spinup time anyway.

    > It's the number of error messages that I'm seeing on the BR burner that's got me most worried,


    Yes, and they wont be happening when all those drives are spinning
    up. Thats the only time that those drives will be taking a lot of current.

    > but also recently I saw a worrying pop-up message from Hard Disk Sentinel that it is predicting an imminent failure of
    > my boot drive too.


    Its notorious for crying wolf.

    > I don't know which of the rails all of these drives are connected to, but if they are all connected to the same rail
    > (very likely) then they might be all sharing current from a diminished resource.


    I doubt it. I bet that if you do total the startup currents for all those
    drives which you havent specified, they wont exceed the surge rating
    of one of the rails. And even if they do, the most that you might see
    is a few slow starts with the worst of the drives which might be what
    HDS is mindlessly screaming about.

    > I wonder how much current each of the optical and hard drives use?


    Its in the datasheets for all of them. You want the startup current.

    You dont need to worry with the optical drive, it will be
    be peanuts compared with the total of the hard drives.

    >>>> That wouldnt normally be the case unless you have one hell of a video card in it.


    >>> Well, the video card is not a monster of any kind, it's more upper mainstream, an AMD Radeon 6870.


    >> Yeah, it only need 2 75W power connectors.


    >> The 12V rails on that power supply are way above what it needs.


    > One or two rails would go to the motherboard, another one would go to the video card,


    Those rails can supply all the video card needs fine.

    The video card needs 150W and each rail can deliver 192W

    > and the last rail would be left for all of the rest of the peripherals.


    Likely. But thats still plenty.

    > I've mostly had no problems with motherboard components (CPU, RAM, PCI cards), no problems with the video card,


    So it must be getting the power it needs.

    > but the rest of the system is all supplied by one rail, such as drives and fans and lights.


    Yes, but even if that rail is a bit overloaded when the hard
    drives are all spinning up at once, the worst that can do is
    see the spinup time a bit longer than it would otherwise be
    with just one drive connected.

    They clearly do spin up.

    > I won't really notice any power problems with the fans or lights, but the drives might be pretty sensitive.


    Nope, they arent at spinnup time and thats the only
    time they are likely to be overloading even one rail.

    >> That power supply handles the video card fine with 2 of the rails
    >> and you have two more for your hard drives which wont take
    >> anything like 384W even if they are all trying to spin up at once.


    > I don't think the video card gets two whole rails to itself.


    The video card datasheet does say it has two power connectors.

    > The motherboard 24-pin connector is one rail which would power the PCI/PCI-e slots, chipset and RAM; and maybe it'll
    > feed a few Watts to the CPU too. Then another 6-pin plug would be a rail for the CPU alone, which also plugs into the
    > motherboard.


    And clearly that works fine.

    > Then a couple of video power connectors would go into the video card, which would likely come from one rail by itself.
    > The video card would also receive some power from the motherboard through the PCI-e slot. So the video card might have
    > at most maybe 1.5 rails for its use (partial motherboard rail & full video rail).


    And it works fine so it must be getting what it needs 12V wise.

    > And the last rail for everything else in the system.


    You dont kinow that with the fans etc particularly.

    Yes, the hard drives may well be on one rail, but that should
    be fine too and the worst you might see is some of the drives
    being a bit slow to spin up, a complete yawn basically.

    It wont be whats producing the symptoms with the optical drive
    because the hard drives will have spun up long before you ever
    write anything with the optical drive and so the current draw of
    the hard drives will be well down on the startup currents.

    >>> and that level is pretty close to the maximum power rating (within 96-97%) of my old PS.


    >> Thats the problem with those power supply 'calculators', they
    >> dont actually calculate what matters, the 12V rail currents.


    >> And the 900W supply you are considering only has 1A more
    >> 12V current available anyway.


    > Well, I'm not really considering a 900W PS, more likely a 750W one.


    So you may not end up with any more 12V current at all.

    >>> When I first obtained this 600W PS, the PS calculator showed that my system requirement was only in the upper 400W
    >>> range.


    >> Do you mean that the calculator has changed, or that
    >> what you have in that system has changed that much ?


    > Yup, the stuff in the system has changed that much. This system is in a constant state of evolution, including the
    > case itself. I upgraded
    > from a mid-tower with a capacity for only four 3.5" drives to one with six 3.5" drives, and then it quickly evolved to
    > to fill up those additional drive slots. Also there was a video card upgrade, and a
    > CPU upgrade along the way too.


    I've never believed those calculators, I calculate the actual rail currents.

    >>> When you add it up, yes the 4 separate rails come

    >> out to about 64A, but the point is is it possible that some of the rails are overloaded by themselves?


    >> Nope, not with that particular video card.


    > I don't think the video card is the issue here at all! Just those
    > drives in combination with all of the other powered peripherals
    > inside that system.


    They arent all necessarily on just one rail and their currents arent
    significant anyway compared with the hard drive startup currents.

    > I played around with the figures in one of the PS calculators, and I found out that it's assuming 13W per 7200-rpm
    > SATA
    > hard drive, 24W per 7200-rpm IDE HDD,


    Thats pretty bogus when what matters is the startup currents.

    > 29W per Blu-Ray burner, 34W per DVD burner.


    Its silly to assume that all blue ray and dvd burners will consume
    the same amount within 1W

    > Based on that I currently have 129W in internal drives alone (4 SATA HDD, 2 IDE HDD, 1 BR).


    And one rail can deliver 192W, bags of margin.

    > When I previously had the dual DVD burners rather than the single Blu-Ray, I had 168W worth of drives!


    Still fine for a 192W rail.

    > This is now starting to explain why my two DVD burners failed simultaneously.


    Nope. Even if the rail was overloaded, and it isnt,
    that wont kill two DVD burners simultaneously.

    > I also have 4x 250mm case fans on the system (they came with the new case). Each is regular fan is rated at 12W, and
    > each LED fan is 13W. Based on that I have 49W worth of fans (3 regular, 1 LED). Adding to the previous figures of 129W
    > and 168W brings them to overall totals of 178W and 217W, respectively!


    Yebbut the hard drives numbers are bogus.

    > If I only have 192W to play with per rail, then I was well over when I had two DVD burners, and I'm sitting on the
    > edge still now.


    Nope, because the worst that might happen is that a couple of the
    hard drives might spin up a little more slowly than they would if they
    were the only drive in the system and thats a complete yawn in practice.

    >>> Would it be easier to distribute the power if there
    >>> was a single larger rail rather than 4 smaller rails?


    >> No, in fact its harder because you cant do a remote sense
    >> so that the highest current rail is seeing 12V at the pins
    >> without increasing what the other connects get at the pins.


    >> Not that that matter much, the specs on the variation in the 12V rails is pretty wide.


    >> And you have the other problem with a single rail too, limiting the
    >> current to say 75A can still see a decent fire with some shorts.


    > That is obviously a worry, and that's why they didn't do this in the past. I'm hoping that now that they are doing it,
    > that they may have found a way to keep it under control these days?


    Nope, it isnt even possible. 75A is one hell of a current at DC.
     
    Rod Speed, Mar 22, 2012
    #12
  13. Yousuf Khan

    Rod Speed Guest

    KR wrote
    > Yousuf Khan <> wrote


    >> I currently have a desktop with a Zalman 600W PS, it was a pretty
    >> nice PS a few years ago when I got it, but now it looks like the
    >> system has been upgraded and grown again, and I'm starting to see
    >> signs that it's not producing enough power for the components
    >> anymore. So I'm looking at the market for bigger PS's, likely 750W+.


    >> When I got the Zalman, multi-rail +12V were the de riguer feature
    >> of the day. Now that I'm shopping for them again, I see that the
    >> manufacturers have done an about-face, and they are advertising the
    >> advantages of single-rail +12V. The old 600W had 4 rails at 16 Amps
    >> each. The new single rails I'm seeing seem to have a rail at
    >> anywhere from 45A to 65A! Why have the manufacturers done the
    >> about-face on single-rail vs. multi-rail?


    > Traditionally it was always considered good practice to separate the power
    > for digital and analog circuits as much as possible to prevent interference.
    > This would especially be the case in audio systems.


    > In the case of a PC, this would mean keeping the supply for motors
    > (such as Hard Drives, CD ROMS etc on a separate circuit, so as to
    > minimise any electrical noise from these from interfering with digital
    > circuits - assuming this really is a problem in a modern PC.


    Thats why there are separate 5V, 3.3V and 12V rails.

    > Usually having separate supply cables from a common power source is sufficient.


    > I would suggest it is more likely done to keep the
    > currents manageable on particular circuits however.


    Particularly when there are separate rails at the same voltage.

    > You might have 60A available, but in cases like this
    > where one circuit is never going to need more than
    > (say) 15a, it is safer to split it into 4 separate circuits.


    Doesnt explain why they have now reverted to a single 12V rail.

    > Exactly the same is done in your home fusebox in having
    > separate fuses and circuits for your lights, power points,
    > air con, water heater, stove etc, rather than just having
    > a single 200A fuse for the entire lot.


    The british do in fact have a single ring main for most of the GPOs.

    That for other reasons tho, particularly minimising the wire guage used
    and making the system more tolerant of poor connections at the GPOs etc.
     
    Rod Speed, Mar 22, 2012
    #13
  14. Yousuf Khan

    PeterC Guest

    On Wed, 21 Mar 2012 18:30:38 -0400, Paul wrote:

    <snip very useful information>
    > The keyword "SELV" comes
    > to mind, but that's about all I remember now.


    "SELV" means, IIRC, "Safe Extra-Low Voltage", often used for light fittings
    in bathrooms etc.
    Bear in mind that "LV", to a mains engineer, means <1000V!
    --
    Peter.
    The gods will stay away
    whilst religions hold sway
     
    PeterC, Mar 22, 2012
    #14
  15. Yousuf Khan

    Yousuf Khan Guest

    On 22/03/2012 2:47 AM, Rod Speed wrote:
    > Yousuf Khan wrote
    >> Rod Speed wrote
    >>> And the 900W supply you are considering only has 1A more
    >>> 12V current available anyway.

    >
    >> Well, I'm not really considering a 900W PS, more likely a 750W one.

    >
    > So you may not end up with any more 12V current at all.


    Unless it's a single-rail, then it'll have a *lot* more 12V current.
    I've been window-shopping, most of the latest high-end PS'es are now all
    single-rail, very few multi-rail left anymore.

    >> I played around with the figures in one of the PS calculators, and I found out that it's assuming 13W per 7200-rpm
    >> SATA
    >> hard drive, 24W per 7200-rpm IDE HDD,

    >
    > Thats pretty bogus when what matters is the startup currents.


    Well, that's likely what they are assuming, the worst-case scenarios,
    which is usually startup currents.

    >> 29W per Blu-Ray burner, 34W per DVD burner.

    >
    > Its silly to assume that all blue ray and dvd burners will consume
    > the same amount within 1W


    It's probably just an average they are taking, or maybe a worst-case.

    >> Based on that I currently have 129W in internal drives alone (4 SATA HDD, 2 IDE HDD, 1 BR).

    >
    > And one rail can deliver 192W, bags of margin.
    >
    >> When I previously had the dual DVD burners rather than the single Blu-Ray, I had 168W worth of drives!

    >
    > Still fine for a 192W rail.
    >
    >> This is now starting to explain why my two DVD burners failed simultaneously.

    >
    > Nope. Even if the rail was overloaded, and it isnt,
    > that wont kill two DVD burners simultaneously.


    But the fact remains that they *did* die simultaneously, so if this is
    not the most likely reason for it, then I invite you to come up with
    another reason.

    >> I also have 4x 250mm case fans on the system (they came with the new case). Each is regular fan is rated at 12W, and
    >> each LED fan is 13W. Based on that I have 49W worth of fans (3 regular, 1 LED). Adding to the previous figures of 129W
    >> and 168W brings them to overall totals of 178W and 217W, respectively!

    >
    > Yebbut the hard drives numbers are bogus.


    Again, I'm just working with the online PS calculator figures here, I
    have no reason to doubt them. So again, if you got better numbers, I
    invite you to present them, and why.

    >> If I only have 192W to play with per rail, then I was well over when I had two DVD burners, and I'm sitting on the
    >> edge still now.

    >
    > Nope, because the worst that might happen is that a couple of the
    > hard drives might spin up a little more slowly than they would if they
    > were the only drive in the system and thats a complete yawn in practice.


    Which is basically the problem that's happening with most of the hard
    drives, but it still counts against the drive as a SMART error in the
    logs regardless. There's no way to tell if a spin retry error is due to
    power supply problems or due to actual mechanical stiction. But
    PS-generated spin retry is easy to fix, and I'd rather leave the spin
    retry errors to detect actual mechanical stiction rather than these
    bogus power problems. Mechanical stiction will tell me that it's really
    time to replace the drives.

    As for the optical drive(s), the errors don't crop up during startup,
    they show up in the Windows Event logs randomly. That means that they
    occur when the system is already up and running and in a steady state or
    even idle. As mentioned, the optical drives are empty most of the time,
    so why they are sending out error messages when there is nothing in them
    is beyond me. I can only assume Windows periodically polls the status of
    these optical drives, and that's when we see these error messages.

    Yousuf Khan
     
    Yousuf Khan, Mar 22, 2012
    #15
  16. On Wed, 21 Mar 2012 19:45:30 -0400, Yousuf Khan
    <> wrote:

    >Well, I ran my system components through a few power supply calculators:
    >
    >http://extreme.outervision.com/PSUEngine said I needed 580W.
    >http://www.thermaltake.outervision.com/Power said I needed 574W.
    >http://support.asus.com/powersupply.aspx said I needed 900W!!!
    >
    >Obviously, the Asus rating is an outlier so I'm ignoring that one, but
    >the other two seem to agree pretty close to each other, and that level
    >is pretty close to the maximum power rating (within 96-97%) of my old
    >PS. And with the age of the PS advancing in years, its maximum capacity
    >might actually be decreasing over time.


    I would get a Kill-A-Watt and see what it's really using.

    I haven't checked mine when the needles are pegged but at normal
    desktop usage I was surprised at how little my UPS says it's
    delivering.
     
    Loren Pechtel, Mar 22, 2012
    #16
  17. Yousuf Khan

    Rod Speed Guest

    Yousuf Khan wrote
    > Rod Speed wrote
    >> Yousuf Khan wrote
    >>> Rod Speed wrote


    >>> I played around with the figures in one of the PS calculators, and I found out that it's assuming 13W per 7200-rpm
    >>> SATA
    >>> hard drive, 24W per 7200-rpm IDE HDD,


    >> Thats pretty bogus when what matters is the startup currents.


    > Well, that's likely what they are assuming, the worst-case scenarios,


    Nope. There is no 2:1 ratio between the startup currents with SATA
    and IDE HDDs, most obviously with the drives available in both formats.

    > which is usually startup currents.


    >>> 29W per Blu-Ray burner, 34W per DVD burner.


    >> Its silly to assume that all blue ray and dvd burners will consume the same amount within 1W


    > It's probably just an average they are taking, or maybe a worst-case.


    It isnt even an average with that silly 1W precision,
    its straight from someone's arse.

    >>> Based on that I currently have 129W in internal drives alone (4 SATA HDD, 2 IDE HDD, 1 BR).


    >> And one rail can deliver 192W, bags of margin.


    >>> When I previously had the dual DVD burners rather than the single Blu-Ray, I had 168W worth of drives!


    >> Still fine for a 192W rail.


    >>> This is now starting to explain why my two DVD burners failed simultaneously.


    >> Nope. Even if the rail was overloaded, and it isnt,
    >> that wont kill two DVD burners simultaneously.


    > But the fact remains that they *did* die simultaneously,


    Yes, but it cant have been due to that rail being overloaded
    with all the hard drives spiinning up at once, because the most
    that will do is see the 12V rail sag a bit for the short time that the
    hard drives are taking the maximum startup current, and a small
    sag in the 12V wont be what killed both drives simultaneously.

    > so if this is not the most likely reason for it,


    It isnt.

    > then I invite you to come up with another reason.


    Dont have to, it cant be that.

    Bet if you actually put a decent max min multimeter on the rail,
    you wont find it sags much at all.

    >>> I also have 4x 250mm case fans on the system (they came with the new case). Each is regular fan is rated at 12W, and
    >>> each LED fan is 13W. Based on that I have 49W worth of fans (3 regular, 1 LED). Adding to the previous figures of
    >>> 129W and 168W brings them to overall totals of 178W and 217W, respectively!


    >> Yebbut the hard drives numbers are bogus.


    > Again, I'm just working with the online PS calculator figures here,


    And that is where you are going wrong. You have to use the real
    startup current numbers from the hard drive datasheets instead.

    > I have no reason to doubt them.


    You have every reason to doubt them on that terminal
    stupidity of a 2:1 ratio between sata and ide drives
    when the same drive is available in both formats alone.

    And you cant just add the DVD and blue ray numbers
    to the hard drive numbers either, because the hard drive
    spinup currents dont happen at the same time that the
    burners are presenting their maximum load to the 12V rails.

    > So again, if you got better numbers,


    I already told you where to get them, from the
    hard drive datasheets, the spinup currents.

    > I invite you to present them,


    Cant do that, you never specified the hard drive model numbers.

    Everest will give them to you without even opening the case.

    > and why.


    I already told you why, repeatedly.

    >>> If I only have 192W to play with per rail, then I was well over
    >>> when I had two DVD burners, and I'm sitting on the edge still now.


    >> Nope, because the worst that might happen is that a couple of the
    >> hard drives might spin up a little more slowly than they would if they were the only drive in the system and thats a
    >> complete yawn in practice.


    > Which is basically the problem that's happening with most of the hard drives,


    I dont believe that with that most claim.

    > but it still counts against the drive as a SMART error in the logs regardless.


    Nope. Its just REPORTING the longer spin up time, it isnt counting against anything.

    > There's no way to tell if a spin retry error is due to power supply problems or due to actual mechanical stiction.


    Corse there is, you run it with just a couple of drives for a test.

    > But PS-generated spin retry is easy to fix, and I'd rather leave the spin retry errors to detect actual mechanical
    > stiction


    You dont get enough mechanical stiction now to matter because
    modern drives unload the heads from the media at shutdown now.

    > rather than these bogus power problems. Mechanical stiction will tell me that it's really time to replace the drives.


    If you see mechanical stiction, the drive wont spin up at all.

    > As for the optical drive(s), the errors don't crop up during startup, they show up in the Windows Event logs randomly.


    So they cant be due to the rail not being adequate.

    > That means that they occur when the system is already up and running and in a steady state or even idle.


    So they cant be due to the rail not being adequate.

    > As mentioned, the optical drives are empty most of the time, so why they are sending out error messages when there is
    > nothing in them is beyond me.


    One obvious possibility, is, as I said, that the
    power supply has too much noise on the 5V rail.

    The only real way to check that possibility if you dont have
    a CRO etc and dont know how to use one is to replace the
    power supply and see if the problem goes away.

    And you dont need anything special power supply wise for that
    test, you can see if the problem goes away with a normal power
    supply by leaving most of the hard drives unplugged for the test.

    > I can only assume Windows periodically polls the status of these optical drives, and that's when we see these error
    > messages.


    Even if it does, it cant be because the rail is overloaded,
    because the hard drives arent spinning up at that time.
     
    Rod Speed, Mar 22, 2012
    #17
  18. Yousuf Khan

    Rod Speed Guest

    Loren Pechtel wrote
    > Yousuf Khan <> wrote


    >> Well, I ran my system components through a few power supply calculators:


    >> http://extreme.outervision.com/PSUEngine said I needed 580W.
    >> http://www.thermaltake.outervision.com/Power said I needed 574W.
    >> http://support.asus.com/powersupply.aspx said I needed 900W!!!


    >> Obviously, the Asus rating is an outlier so I'm ignoring that one,
    >> but the other two seem to agree pretty close to each other, and that
    >> level is pretty close to the maximum power rating (within 96-97%) of
    >> my old PS. And with the age of the PS advancing in years, its
    >> maximum capacity might actually be decreasing over time.


    > I would get a Kill-A-Watt and see what it's really using.


    That doesnt tell you if a particular rail is getting overloaded.

    You need a multimeter on the individual rails to check that.

    > I haven't checked mine when the needles are pegged but at normal
    > desktop usage I was surprised at how little my UPS says it's delivering.


    Thats normal.
     
    Rod Speed, Mar 22, 2012
    #18
  19. Yousuf Khan

    Yousuf Khan Guest

    On 22/03/2012 3:29 PM, Loren Pechtel wrote:
    > I would get a Kill-A-Watt and see what it's really using.


    I actually did get one at one time, but it turned out to be bad, so I
    returned it, and I never bothered again.

    Yousuf Khan
     
    Yousuf Khan, Mar 22, 2012
    #19
  20. Yousuf Khan

    Charlie Guest


    >
    > As for the optical drive(s), the errors don't crop up during startup,
    > they show up in the Windows Event logs randomly.


    I had the same thing and cured it by raising the CPU voltage slightly.

    Charlie
     
    Charlie, Mar 23, 2012
    #20
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