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Power supplies?



 
 
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  #11  
Old March 24th 09, 04:53 AM posted to comp.sys.ibm.pc.hardware.chips
YKhan
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Posts: 266
Default Power supplies?

On Mar 23, 5:33*pm, daytripper wrote:
It's nothing that involved - there's no "trapped" electrons, and there's no
real effect on "efficiency" in any classic sense. That whole spiel simply
points out the effect of "partitioning" 12V capacity into multiple isolated
rails, verses having all 12V capacity on a single rail.


And you mentioned that UL & CSA safety requirements don't allow for
more than 240VA, which would mean a maximum of 20A @ 12V. So I don't
see how they can avoid having multiple rails if they want more than
240VA on the system?

For instance, say you have a single-rail supply with 36A of 12V capacity, and
another supply with 2 12V rails rated at 18A each. Now build a system that
requires 12A of 12V for the motherboard and peripherals, plus a pair of 12A
graphics cards.

Both supplies are rated at 36A of 12V, but hooking up the dual-rail supply is
probably going to be more challenging than the single rail supply. In fact, it
probably could not be done - hence you would have unusable ("trapped")
capacity in the dual-rail supply...


But that's probably why they have triple rail power supplies.

Yousuf Khan
  #12  
Old March 24th 09, 05:25 AM posted to comp.sys.ibm.pc.hardware.chips
daytripper
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Posts: 265
Default Power supplies?

On Mon, 23 Mar 2009 20:53:38 -0700 (PDT), YKhan wrote:

On Mar 23, 5:33*pm, daytripper wrote:
It's nothing that involved - there's no "trapped" electrons, and there's no
real effect on "efficiency" in any classic sense. That whole spiel simply
points out the effect of "partitioning" 12V capacity into multiple isolated
rails, verses having all 12V capacity on a single rail.


And you mentioned that UL & CSA safety requirements don't allow for
more than 240VA, which would mean a maximum of 20A @ 12V. So I don't
see how they can avoid having multiple rails if they want more than
240VA on the system?

For instance, say you have a single-rail supply with 36A of 12V capacity, and
another supply with 2 12V rails rated at 18A each. Now build a system that
requires 12A of 12V for the motherboard and peripherals, plus a pair of 12A
graphics cards.

Both supplies are rated at 36A of 12V, but hooking up the dual-rail supply is
probably going to be more challenging than the single rail supply. In fact, it
probably could not be done - hence you would have unusable ("trapped")
capacity in the dual-rail supply...


But that's probably why they have triple rail power supplies.

Yousuf Khan


And more, even. As we all know, "size matters" ;-)

Bottom line is you can't simply buy capacity - a box of watts - without
understanding potential partitioning effects as applied to a given system
build...

/daytripper
  #13  
Old March 24th 09, 10:27 AM posted to comp.sys.ibm.pc.hardware.chips
Robert Redelmeier
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Posts: 316
Default Power supplies?

daytripper wrote in part:
It's nothing that involved - there's no "trapped" electrons,
and there's no real effect on "efficiency" in any classic
sense. That whole spiel simply points out the effect of
"partitioning" 12V capacity into multiple isolated rails,
verses having all 12V capacity on a single rail.


For instance, say you have a single-rail supply with 36A
of 12V capacity, and another supply with 2 12V rails rated
at 18A each. Now build a system that requires 12A of 12V
for the motherboard and peripherals, plus a pair of 12A
graphics cards.


Both supplies are rated at 36A of 12V, but hooking up the
dual-rail supply is probably going to be more challenging
than the single rail supply. In fact, it probably could
not be done - hence you would have unusable ("trapped")
capacity in the dual-rail supply...



I thought there was a serious problem with underloading
(5%) a switcher (or any given rail) in that the transistor
switch-on was very short and there were LC reactances that
made regulation difficult.

-- Robert

  #14  
Old March 24th 09, 05:20 PM posted to comp.sys.ibm.pc.hardware.chips
YKhan
external usenet poster
 
Posts: 266
Default Power supplies?

On Mar 24, 12:25*am, daytripper wrote:
On Mon, 23 Mar 2009 20:53:38 -0700 (PDT), YKhan wrote:
But that's probably why they have triple rail power supplies.


And more, even. As we all know, "size matters" ;-)


Yeah, well the one I'm looking at is seriously blinged-out. Quad-rails
and blue LEDs and all. :-)

::: Zalman, leading the world of Quiet Computing Solutions :::
http://www.zalman.co.kr/eng/product/...ad.asp?Idx=196

It's a refurbed unit though, so it's a good deal.

Yousuf Khan
  #15  
Old March 28th 09, 10:07 PM posted to comp.sys.ibm.pc.hardware.chips
Scott Alfter
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Posts: 52
Default Power supplies?

In article , Yousuf Khan wrote:
It's possibly time to upgrade my power supply. Haven't shopped around
for one in ages. What's the new features that I have to look for these
days? My last PS was a 450W ATX from maybe 5 years ago. I expect my new
one would have to be at least 500W now.


Why? I have seen power supplies at Fry's rated for 1 kW (!) and up, but how
much of this is actually needed by the average system and how much of it is
little more than stuff to enable dick-size contests among gamers? My
fastest system is a Core 2 Quad Q6600 with a couple of hard drives and a
9500GT; it runs just fine on a 380W power supply (Antec Earthwatts, if
you're curious). I've built servers with sixteen hard drives configured as
hardware RAID-5, and a 650W RPS is sufficient for that (staggered spin-up
helps here).

Getting a good-quality power supply from a reputable vendor is more
important than going for the biggest number. The high-efficiency power
supplies that have become available in the past year or two (look for "80
Plus" on the box), in addition to using less power for a given output, also
run cooler, which should help them last longer.

_/_
/ v \ Scott Alfter (remove the obvious to send mail)
(IIGS( http://alfter.us/ Top-posting!
\_^_/ rm -rf /bin/laden What's the most annoying thing on Usenet?

  #16  
Old March 29th 09, 08:49 PM posted to comp.sys.ibm.pc.hardware.chips
Yousuf Khan
external usenet poster
 
Posts: 914
Default Power supplies?

Scott Alfter wrote:
In article , Yousuf Khan wrote:
It's possibly time to upgrade my power supply. Haven't shopped around
for one in ages. What's the new features that I have to look for these
days? My last PS was a 450W ATX from maybe 5 years ago. I expect my new
one would have to be at least 500W now.


Why? I have seen power supplies at Fry's rated for 1 kW (!) and up, but how
much of this is actually needed by the average system and how much of it is
little more than stuff to enable dick-size contests among gamers? My
fastest system is a Core 2 Quad Q6600 with a couple of hard drives and a
9500GT; it runs just fine on a 380W power supply (Antec Earthwatts, if
you're curious). I've built servers with sixteen hard drives configured as
hardware RAID-5, and a 650W RPS is sufficient for that (staggered spin-up
helps here).

Getting a good-quality power supply from a reputable vendor is more
important than going for the biggest number. The high-efficiency power
supplies that have become available in the past year or two (look for "80
Plus" on the box), in addition to using less power for a given output, also
run cooler, which should help them last longer.


Well because I've been having some errors on my hard drives (another
thread on another newsgroup), especially when I added more hard drives
to the system. The drive problems ranged from the firmware puking its
guts out to pending sectors waiting to be remapped but never remapping.

My existing 420W unit was from long before the current ATX12V 2.x era.
So it seemed like a good place to start to resolve these issues. I
personally resisted the power-supply as the solution for a long time, as
it seems like the default solution to every problem these days. But I'm
getting the feeling it may have some validity in my case.

Yousuf Khan
 




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