Overclock.net › Forums › Components › Power Supplies › Can the unused amps on multiple rail PSUs really be combined?
New Posts  All Forums:Forum Nav:

Can the unused amps on multiple rail PSUs really be combined? - Page 2

post #11 of 16
I'll say go with the PC Power & Cooling 610 40a on one rail. I do have a video card the sucks up 215w the hd2900xt. And it a great PSU. I just order the PC Power & Cooling 750w for my new built even tho the 610w would have been ok if I decide to go xfire on the hd3870 that I be getting.
Yin
(17 items)
 
  
CPUMotherboardGraphicsRAM
Intel i7 4790k 4.7@1.265 Asus Sabertooth Z87 2 X GALAX GeForce GTX 980 HOF 4GB SLI 4x4gb G.Skill Trident X 
Hard DriveHard DriveHard DriveCooling
Samsung 850 500gigs Samsung 840  2 PNY SSD 240gig Switech H220x 
OSMonitorKeyboardPower
Windows 7 Ultimate 64bit/Windows 8.1/Windows10/... ASUS 24" Logitech G15 Consair HX750 
CaseMouseAudio
Antec P280 LOGITECH G502 PROTEUS CORE Sound Blaster Z 
  hide details  
Reply
Yin
(17 items)
 
  
CPUMotherboardGraphicsRAM
Intel i7 4790k 4.7@1.265 Asus Sabertooth Z87 2 X GALAX GeForce GTX 980 HOF 4GB SLI 4x4gb G.Skill Trident X 
Hard DriveHard DriveHard DriveCooling
Samsung 850 500gigs Samsung 840  2 PNY SSD 240gig Switech H220x 
OSMonitorKeyboardPower
Windows 7 Ultimate 64bit/Windows 8.1/Windows10/... ASUS 24" Logitech G15 Consair HX750 
CaseMouseAudio
Antec P280 LOGITECH G502 PROTEUS CORE Sound Blaster Z 
  hide details  
Reply
post #12 of 16
Thread Starter 
If it's true that the PSU has a seperate rail for the PCI-e connector and that it delivers enough amp to the video card, then there won't be a problem. I assume the biggest misinformation is that people assume that you just combine the amps for all rails for the toal amperage, but the total amount of amps is always LESS because of wasted power.

.
post #13 of 16
Quote:
Originally Posted by aweir View Post
If it's true that the PSU has a seperate rail for the PCI-e connector and that it delivers enough amp to the video card, then there won't be a problem. I assume the biggest misinformation is that people assume that you just combine the amps for all rails for the toal amperage, but the total amount of amps is always LESS because of wasted power.

.
That part is true. Thats why I decided to stick the the one rail psu. Thats just me.
Yin
(17 items)
 
  
CPUMotherboardGraphicsRAM
Intel i7 4790k 4.7@1.265 Asus Sabertooth Z87 2 X GALAX GeForce GTX 980 HOF 4GB SLI 4x4gb G.Skill Trident X 
Hard DriveHard DriveHard DriveCooling
Samsung 850 500gigs Samsung 840  2 PNY SSD 240gig Switech H220x 
OSMonitorKeyboardPower
Windows 7 Ultimate 64bit/Windows 8.1/Windows10/... ASUS 24" Logitech G15 Consair HX750 
CaseMouseAudio
Antec P280 LOGITECH G502 PROTEUS CORE Sound Blaster Z 
  hide details  
Reply
Yin
(17 items)
 
  
CPUMotherboardGraphicsRAM
Intel i7 4790k 4.7@1.265 Asus Sabertooth Z87 2 X GALAX GeForce GTX 980 HOF 4GB SLI 4x4gb G.Skill Trident X 
Hard DriveHard DriveHard DriveCooling
Samsung 850 500gigs Samsung 840  2 PNY SSD 240gig Switech H220x 
OSMonitorKeyboardPower
Windows 7 Ultimate 64bit/Windows 8.1/Windows10/... ASUS 24" Logitech G15 Consair HX750 
CaseMouseAudio
Antec P280 LOGITECH G502 PROTEUS CORE Sound Blaster Z 
  hide details  
Reply
post #14 of 16
What wasted power?

Note that multi-rail PSUs originally appeared to comply with a EU directive (which stated that any 12V rail should deliver no more than 20A...), which then became part of the ATX12V standard. Later, this requirement was dropped, and now we see PSUs with higher current rails (including single rails). Obviously, marketing folks took off, and stated that multi-rails PSUs were superior.

You are right that on a multi-rail PSU the sum of the rails is often higher than the total rated wattage of the PSU, but that's NOT because power is 'wasted'. This is designed so on purpose. If a 600W PSU that delivers 44A on the 12V rails has four rails, you'll see that each rail is rated more than the expected 11A (if divided by four). Thus, each 12V rail can deliver, say, 18A, but all 12V rails combined can only deliver 44A. If you draw 18A from one rail (not sure how to accomplish that.. that's beastly), there is only 44-18 = 26A left for the remaining three rails. It's therefore important to always check what the TOTAL available current on the 12V rails is.

Again, a well built multi rail PSU isn't any better or worse than a well built single rail PSU. I can mention very nice multi rail PSUs (see my system specs), and very nice single rail PSUs (the afore mentioned PC P&C silencer, some of the Silverstone OP/DA series PSUs, Corsair HX series...)
    
CPUMotherboardGraphicsRAM
E8400 @ 3.8 GHz DFI LANPARTY DK X38-T2R eVGA 8400GS 2GB Mushkin DDR2 800 (single stick) 
Hard DriveOptical DriveOSMonitor
250GB WD SATA None Windows XP Pro 32-bit HP Pavilion f1703 
KeyboardPowerCaseMouse
N/A Corsair HX520 Coolermaster Cavalier N/A 
Mouse Pad
N/A 
  hide details  
Reply
    
CPUMotherboardGraphicsRAM
E8400 @ 3.8 GHz DFI LANPARTY DK X38-T2R eVGA 8400GS 2GB Mushkin DDR2 800 (single stick) 
Hard DriveOptical DriveOSMonitor
250GB WD SATA None Windows XP Pro 32-bit HP Pavilion f1703 
KeyboardPowerCaseMouse
N/A Corsair HX520 Coolermaster Cavalier N/A 
Mouse Pad
N/A 
  hide details  
Reply
post #15 of 16
Visual aid:

Once again...
(13 items)
 
  
CPUMotherboardGraphicsRAM
i7 920 [4.28GHz, HT] Asus P6T + Broadcom NetXtreme II VisionTek HD5850 [900/1200] + Galaxy GT240 2x4GB G.Skill Ripjaw X [1632 MHz] 
Hard DriveOSMonitorKeyboard
Intel X25-M 160GB + 3xRAID0 500GB 7200.12 Window 7 Pro 64 Acer H243H + Samsung 226BW XARMOR-U9BL  
PowerCaseMouseMouse Pad
Antec Truepower New 750W Li Lian PC-V2100 [10x120mm fans] Logitech G9 X-Trac Pro 
  hide details  
Reply
Once again...
(13 items)
 
  
CPUMotherboardGraphicsRAM
i7 920 [4.28GHz, HT] Asus P6T + Broadcom NetXtreme II VisionTek HD5850 [900/1200] + Galaxy GT240 2x4GB G.Skill Ripjaw X [1632 MHz] 
Hard DriveOSMonitorKeyboard
Intel X25-M 160GB + 3xRAID0 500GB 7200.12 Window 7 Pro 64 Acer H243H + Samsung 226BW XARMOR-U9BL  
PowerCaseMouseMouse Pad
Antec Truepower New 750W Li Lian PC-V2100 [10x120mm fans] Logitech G9 X-Trac Pro 
  hide details  
Reply
post #16 of 16
[quote=aweir;3660176]you even said it yourself...

Quote:
Originally Posted by aweir View Post
Or can their only be "true" dual rail PSUs? Can there be such a thing as a PSU with 4 INDEPENDENT rails?
I said two. You said four. I have never seen one with true four rails. Only two. Even if those two rails are split into four or more, there's still only truly four +12V rails.

Quote:
Originally Posted by aweir View Post
If it's true that the PSU has a seperate rail for the PCI-e connector and that it delivers enough amp to the video card, then there won't be a problem. I assume the biggest misinformation is that people assume that you just combine the amps for all rails for the toal amperage, but the total amount of amps is always LESS because of wasted power.
Right... The rails aren't additive. You have to remember that the per-rail measurement is a designation of where the OCP (over current protection) is set. NOT a measurement of capability, therefore they're not additive. Only the "total combined output" rating as stated on the label is your actual +12V capability.

There's a mis-conception that "multiple +12V rails are a hassle because you have to figure out what needs to plug in where" but the fact of the matter is that most PSU's have all similar connectors on the same rail. Or in the case of multiple PCIe connectors like 2, 4 or 6, may group a pair of PCIe on a rail and nothing else. See the "examples" toward the end of my FAQ post. Jockeying connectors yields nothing in most cases. And each rail should have it's OCP set to nearly twice what the connectors on that rail would ever need.

Quote:
Originally Posted by DuckieHo View Post
Visual aid...
Always diggin' the visual aid, Duckie.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Power Supplies
Overclock.net › Forums › Components › Power Supplies › Can the unused amps on multiple rail PSUs really be combined?