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#11
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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
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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
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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
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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
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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
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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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