• Welcome to TechPowerUp Forums, Guest! Please check out our forum guidelines for info related to our community.

Dual-rail PSU: Yes or no?

Joined
May 14, 2006
Messages
997 (0.23/day)
Likes
13
Location
Kentucky
System Name Sony Vaio - VGNFW390-CTO
Processor Intel® Core™ 2 Duo Processor T9550 (2.66GHz)
Cooling Stock
Memory 4GB DDR2-SDRAM (DDR2-800, 2GBx2)
Video Card(s) ATI Mobility Radeon™ HD 3650 with 512MB vRAM (pitiful card)
Storage 320GB SATA Hard Disk Drive [7200 rpm]
Display(s) LCD 16.4" (XBRITE-FullHD™)
Audio Device(s) SupremeFX
Software Windows 7
#1
I'm looking to upgrade my PSU because I want to get new graphics cards and I realized that my 600W PSU only has 23 Amperes on the 12V rail which is WAY under the suggested amount. I've seen the PSUs with the Dual-rail and single rail for the 12V. Which is better to buy?
 

Tatty_One

Super Moderator
Staff member
Joined
Jan 18, 2006
Messages
19,823 (4.52/day)
Likes
6,102
Location
Worcestershire, UK
Processor Skylake Core i7 6700k @ 4.6gig
Motherboard MSI Z170A Tomahawk
Cooling Cooler Master Seidon 240V AIO/Viper140's
Memory 16GB Corsair Vengeance LPX 3000mhz CL14
Video Card(s) Sapphire 4gb R9 290X VaporX @1150mhz
Storage SkHynix SL308 120GB/CrucialM4/1TB WD Black
Display(s) LG 29inch 2560x1080 Curved Ultrawide IPS
Case Phanteks Enthoo Pro M Windowed - Gunmetal
Audio Device(s) Xifi Elite Pro 7.1/VideoLogic ZXR550's
Power Supply XFX Pro Black Edition 750W Gold modular
Keyboard CM Storm Octane Combo
Software Win 10 Home x64
#2
Everyone will have their own opinion on this, I can only speak from my experiences and I have only EVER had problems with dual rails and I have owned an Antec and a Tagan so not just cheap units.

The way I see it, usually in a dual rail setup you have one rail looking after the CPU and the other rail for the rest, lets say you have around 21Amp on each rail, with the CPU rail you may be using just 12 Amps so you have 9 Amps spare, on the other rail you have everything else drawing power, now my old 1800XT overclocked with extra volts at load was drawing up to 16+Amps, combine that with everything else and if you hit or exceed the 21Amps for prolonged intervals......BANG! even tho you have those unusued amps on the other rail. Now I know thats its not quite as simple as that but in basic terms you can lose your PSU on a dual rail when not using all the power, on a single rail providing you are buying a unit that is powerful enough you have ALL power on tap.

See my specs, my last dual rail was a 550W dual rail Tagan ( with 22 and 20 Amp rails)and it lasted me 3 months before it blew. Now perhaps I have just been unlucky but I am and will continue to be a single rail man.
 
Joined
Dec 6, 2005
Messages
9,941 (2.25/day)
Likes
3,894
Location
Manchester, NH
System Name Working on it ;)
Processor I7-4790K
Motherboard MSI Z97 U3 Plus
Cooling Be Quiet Pure Rock Air
Memory 16GB 4x4 G.Skill CAS9 2133 Sniper
Video Card(s) Power Color RD Vega 64 Reference
Storage Samsung EVO 500GB / 8 Different WDs / NAS with 2x2Tb WD Black
Display(s) 34" LG 34CB88-P 21:9 Curved UltraWide QHD (3440*1440)
Case Rosewill Challenger
Audio Device(s) Onboard + HD HDMI
Power Supply Corsair HX750 (love it)
Mouse Logitech G5
Keyboard Logitech G710 Blue / G610 Orion Red
Software Win 7 Pro
#3
Everyone will have their own opinion on this
Indeed :) I've asked a similar question and gotten all sorts of answers, but from what I gather, the rails are shared amongst the power connectors. I don't think there's a problem with having 2 rails at all... and, in effect, you have descreet redundant supplies with each rail if they are shared.

OT - I'd go with modular cables any day.

I have recently worked with:
Hiper 580w (typeR) - I own it.. very nice supply, cables are OK, but have "dongled" extension connectors which are a pain.
http://www.newegg.com/Product/Product.asp?Item=N82E16817128001

KINGWIN ABT-600MA1 600W - did a build for a freind, and found this to have the absolute best cabling system. Decent reputation.
http://www.newegg.com/Product/Product.asp?Item=N82E16817121012
 

bruins004

New Member
Joined
Sep 27, 2005
Messages
2,479 (0.55/day)
Likes
74
Processor AMD Athlon 64 3200+ (939)
Motherboard MSI Neo K8n Neo4-F with Nforce 4
Cooling ThermalTake Venus12 + 3 case fans + PCI slot cooler for GPU
Memory 2x 512mb Kingston PC-3200
Video Card(s) XFX GeForce 7800GT
Storage Western Digital 160GB
Display(s) ViewSonic VX2025WM
Case Logisys Dracula Case (Black)
Audio Device(s) Onboard Sound, Logitech X-530 Surround Sound Speakers
Power Supply OCZ PowerStream 520W
Software Window XP Pro, Office Suite, Tons of Games
#4
Its very easy to understand the difference.

As said above, dual rails will have each rail supply power to different parts of the computer.
For most it is 1 rail supplies power to the CPU while the rest supplies power to the rest of the computer.
Unfort. the unused amps on rails cannot be used by the other rail.
However, this does allow for a more consistent flow of power throughout the computer.

Same idea works with three rails. The only difference is there is a rail just for the GPU, the CPU and then the rest of the computer.
The other problem related to multi-railed PSUs is if one rail dies, the PSU will still work, but the computer will act wierd and not work properly. Therefore, it is a little harder to tell if the PSU is working correctly or not.

With a single rail there is some more overhead in the loss of power (amps), however, if the rail dies, the PSU is dead. Much easier to tell. So just like everything else, there are pros and cons to both.

A better idea isnt to base your selection on if it is multi or single railed.
You should base it on the brand and the amps in the PSU.
FSP, Hyper, OCZ and PC Power and Cooling are very well known and reputible brands.
I would of have put Antec on there, but it seems they are lacking with their quality these days and I refuse to put them up there.
Plus these brands offer very competitive prices with Antec and often perform better.



PS ----> I recommend getting a PSU with at least 32A on the 12V rail. This will allow you to upgrade without getting a new PSU again. With power requirements going up for GPUs, it cannot hurt to not strain your PSU the entire time. :)
 

tigger

I'm the only one
Joined
Mar 20, 2006
Messages
10,476 (2.43/day)
Likes
1,673
System Name Black to the Core MKIV
Processor Intel I7 6700k
Motherboard Asus Z170 Pro Gaming socket 1151
Cooling NZXT Kraken X61 280mm radiator
Memory 2x8gb Corsair vengeance LPX 2400 DDR4
Video Card(s) XFX Radeon R9 290 4gb ddr5
Storage Patriot Blast 120gb ssd Boot and WD10EADX-22TDHB0 1TB Data
Display(s) Dell 2408WFP 24" 1920x1200
Case Nzxt IS 340
Audio Device(s) Asus xonar dsx pci-e
Power Supply Corsair CX750
Mouse Logitech G502
Software Win 10 Pro x64
#5
are'nt most new psu's duel rail+ now anyway?
 
Joined
Dec 6, 2005
Messages
9,941 (2.25/day)
Likes
3,894
Location
Manchester, NH
System Name Working on it ;)
Processor I7-4790K
Motherboard MSI Z97 U3 Plus
Cooling Be Quiet Pure Rock Air
Memory 16GB 4x4 G.Skill CAS9 2133 Sniper
Video Card(s) Power Color RD Vega 64 Reference
Storage Samsung EVO 500GB / 8 Different WDs / NAS with 2x2Tb WD Black
Display(s) 34" LG 34CB88-P 21:9 Curved UltraWide QHD (3440*1440)
Case Rosewill Challenger
Audio Device(s) Onboard + HD HDMI
Power Supply Corsair HX750 (love it)
Mouse Logitech G5
Keyboard Logitech G710 Blue / G610 Orion Red
Software Win 7 Pro
#6
Regarding sharing rails...

Here's a great article on the topic - I guess each one of us is right in some way, but no one is completely correct, and each PSU could be different:

http://www.guru3d.com/article/psu/389/3/
 
Joined
Dec 6, 2005
Messages
9,941 (2.25/day)
Likes
3,894
Location
Manchester, NH
System Name Working on it ;)
Processor I7-4790K
Motherboard MSI Z97 U3 Plus
Cooling Be Quiet Pure Rock Air
Memory 16GB 4x4 G.Skill CAS9 2133 Sniper
Video Card(s) Power Color RD Vega 64 Reference
Storage Samsung EVO 500GB / 8 Different WDs / NAS with 2x2Tb WD Black
Display(s) 34" LG 34CB88-P 21:9 Curved UltraWide QHD (3440*1440)
Case Rosewill Challenger
Audio Device(s) Onboard + HD HDMI
Power Supply Corsair HX750 (love it)
Mouse Logitech G5
Keyboard Logitech G710 Blue / G610 Orion Red
Software Win 7 Pro
#7
are'nt most new psu's duel rail+ now anyway?
Yes, and in all my shopping, I've never seen a single rail above 20A, although I'm sure they are out there. That article above explains why.
 

tigger

I'm the only one
Joined
Mar 20, 2006
Messages
10,476 (2.43/day)
Likes
1,673
System Name Black to the Core MKIV
Processor Intel I7 6700k
Motherboard Asus Z170 Pro Gaming socket 1151
Cooling NZXT Kraken X61 280mm radiator
Memory 2x8gb Corsair vengeance LPX 2400 DDR4
Video Card(s) XFX Radeon R9 290 4gb ddr5
Storage Patriot Blast 120gb ssd Boot and WD10EADX-22TDHB0 1TB Data
Display(s) Dell 2408WFP 24" 1920x1200
Case Nzxt IS 340
Audio Device(s) Asus xonar dsx pci-e
Power Supply Corsair CX750
Mouse Logitech G502
Software Win 10 Pro x64
#8

mikek75

New Member
Joined
Aug 28, 2006
Messages
1,370 (0.33/day)
Likes
116
Location
Chippenham, Wilts, United Kingdom
System Name As easy as falling off a lorry
Processor Core I5 2500K auto tuned to 4.2ghz
Motherboard Gigabyte Z68XP-UD3P
Cooling Corsair H80 sealed water cooler
Memory 16gb Gskill Ripjawz 1600mhz
Video Card(s) XFX 6970 2GB
Storage Corsair 120GB Force 3 SSD, OCZ 60 GB Agility 3 SSD, Seagate 500GB, 2x80gb Maxtors
Display(s) DELL 2309w 23" Widescreen 1920x1080+ LG M2294D 22" 1680x1050 LCDtv/monitor
Case Zalman Z9 Plus
Audio Device(s) X-Fi Xtreme Gamer Fatal1ty Pro
Power Supply PC Power&Cooling 750w Silencer Quad PCIe
Software Windows 7 x64 Home Premium
#9
Well, just to further muddy the waters, I'm an advocate of the booster! I have an Enermax (one for the quality brand list) 535w, which has two 18A rails and a sustained 34A output. When I got my X1950Pro I wanted to make sure I had plenty of juice, so I bought the FSP Booster X3. This has 2*12.5A rails, one for each card, with a signal wire to the main PSU to tell it when to switch on. I only have the one card at the mo, so only one rail was used.

This lasted half a day. Went to switch on my new build the morning after, garbled screen. Direct connection to main PSU, no problem at all. RMA'd back to SCAN who told me it was fine!

Decided to try the ThermalTake Power Express 250W booster. This has a connection to the 24 Pin connector from the main PSU and has two 10A rails (peak 12.5). Basically it boosts the non-cpu rail by 10A for one card or 20A for crossfire, effectivly giving 28A or 38A on a single rail. Been using it for about three weeks now, system completely stable and my card runs 43idle 65load. Only downside with it is extra cabling, but I can live with that!
 
V

v-zero

Guest
#10
Dual rails and Quad rails make more sense than mega single rails, since wiring gets hotter because of current, not voltage...
 

Tatty_One

Super Moderator
Staff member
Joined
Jan 18, 2006
Messages
19,823 (4.52/day)
Likes
6,102
Location
Worcestershire, UK
Processor Skylake Core i7 6700k @ 4.6gig
Motherboard MSI Z170A Tomahawk
Cooling Cooler Master Seidon 240V AIO/Viper140's
Memory 16GB Corsair Vengeance LPX 3000mhz CL14
Video Card(s) Sapphire 4gb R9 290X VaporX @1150mhz
Storage SkHynix SL308 120GB/CrucialM4/1TB WD Black
Display(s) LG 29inch 2560x1080 Curved Ultrawide IPS
Case Phanteks Enthoo Pro M Windowed - Gunmetal
Audio Device(s) Xifi Elite Pro 7.1/VideoLogic ZXR550's
Power Supply XFX Pro Black Edition 750W Gold modular
Keyboard CM Storm Octane Combo
Software Win 10 Home x64
#11
Yes, and in all my shopping, I've never seen a single rail above 20A, although I'm sure they are out there. That article above explains why.
Mine is and thats True not peak power.
 
Joined
May 15, 2006
Messages
4,677 (1.10/day)
Likes
86
Location
Someone who's going to find NewTekie1 and teach hi
Processor DualCore AMD Athlon 64x2 4800+ (o/c 2801mhz STABLE (Ketxxx, POGE, Tatty One, ME))
Motherboard ASUS A8N-SLI Premium (PCIe x16, x4, x1)
Cooling PhaseChange Coolermaster CM754/939 (fan/heatsink), Thermalright heatspreaders + fan built on (RAM)
Memory 512mb PC-3200 DDR400 (set DDR-33 for o/c) by Corsair (matched pair, 2x256mb) 200.1/200mhz
Video Card(s) BFG GeForce 7900 GTX OC 512mb GDDR3 ram (o/c manually to 686 core/865 memory) - PhaseChange cooled
Storage Dual "Raptor X" 16mb 10krpm/RAID 0 Promise EX8350 x4 PCIe 128mb & Intel IO chip/CENATEK RocketDrive
Display(s) SONY 19" Trinitron MultiScan 400ps 1600x1200 75hz refresh 32-bit color
Case Antec Super-LanBoy (aluminum baby-tower w/ lower front & upper rear cooling exhaust fans)
Audio Device(s) RealTek AC97 onboard mobo stereo sound (Altec Lansing ACS-45 speakers - 10 yrs. still running!)
Power Supply Antec 500w ATX 2.0 "SmartPower" powersupply
Software Windows Server 2003 SP #1 fully patched, & massively tuned/tweaked to-the-max (plus latest drivers)
#12
GOOD READ!

For me @ least...

:)

* This is one area I am really "in the dark" about & wondered about since I saw talk of it here before, but nothing SPECIFIC about this particular area of PS' @ least, which I can recall!

APK

P.S.=> The peak power rating stuff I have seen tell of before, how some of them only do that during certain temp ranges iirc, & what-not, but the rails stuff? Whoosh... was over my head/ outta my realm of experience... no longer now, thanks guys! apk
 

Tatty_One

Super Moderator
Staff member
Joined
Jan 18, 2006
Messages
19,823 (4.52/day)
Likes
6,102
Location
Worcestershire, UK
Processor Skylake Core i7 6700k @ 4.6gig
Motherboard MSI Z170A Tomahawk
Cooling Cooler Master Seidon 240V AIO/Viper140's
Memory 16GB Corsair Vengeance LPX 3000mhz CL14
Video Card(s) Sapphire 4gb R9 290X VaporX @1150mhz
Storage SkHynix SL308 120GB/CrucialM4/1TB WD Black
Display(s) LG 29inch 2560x1080 Curved Ultrawide IPS
Case Phanteks Enthoo Pro M Windowed - Gunmetal
Audio Device(s) Xifi Elite Pro 7.1/VideoLogic ZXR550's
Power Supply XFX Pro Black Edition 750W Gold modular
Keyboard CM Storm Octane Combo
Software Win 10 Home x64
#13
Dual rails and Quad rails make more sense than mega single rails, since wiring gets hotter because of current, not voltage...
Therefore in a good quality single rail PSU you get better thermal protection/dissapation so its not an issue. As I said before, I am only talking from personal experience and the only time I have been let down by a PSU is on dual rails, the Targan cost me £70 for gods sake, they are quality kit, the ANtec, well mid range stuff but still not bad.
 
Joined
Oct 15, 2006
Messages
2,341 (0.57/day)
Likes
96
Location
Tyne & Wear, UK
System Name AMD '13
Processor FX-6300 @ 4.43GHz (1.35v)
Motherboard Gigabyte GA-970A-DS3 rev 1.0 (F6)
Cooling Cooler Master T2 + x2 case fans
Memory 2x4Gb Crucial Ballistix Sport DDR3-1600 (Stock)
Video Card(s) Gigabyte GTX650 Ti OC 2Gb @ 1110/1500
Storage Corsair 240Gb SSD / Seagate 500Gb HDD + old skool IDE HDD's x 3
Display(s) Acer 23'' LED
Case Billy Basic
Audio Device(s) Onboard 8.1 HD
Power Supply Corsair CX600
Software Windows 7 Ultimate x64
Benchmark Scores Smenchmarks
#14
Yes, and in all my shopping, I've never seen a single rail above 20A, although I'm sure they are out there. That article above explains why.
Thats interesting, I thought my was single as its 24a, but I guess not! :confused:
 

FLY3R

New Member
Joined
Feb 24, 2006
Messages
395 (0.09/day)
Likes
41
Processor AMD 3700+ SD Core @ 2.8gHz
Motherboard DFI LanParty nf4 Expert
Cooling Zalman
Memory G.Skill Extreme Series (2x 1GB) PC4000
Video Card(s) Evga 7800GT
Storage 80GB Seagate
Display(s) ViewSonic 20.1" Widescreen 16:9
Case CoolerMaster Centron
Audio Device(s) Audigy 2 ZS Gamer
Power Supply SeaSonic 600w SLI
Software XP pro (sp2)
#15
I would deffintly go with a dual rail PSU, personly i think they are more stable.
 
Joined
May 15, 2006
Messages
4,677 (1.10/day)
Likes
86
Location
Someone who's going to find NewTekie1 and teach hi
Processor DualCore AMD Athlon 64x2 4800+ (o/c 2801mhz STABLE (Ketxxx, POGE, Tatty One, ME))
Motherboard ASUS A8N-SLI Premium (PCIe x16, x4, x1)
Cooling PhaseChange Coolermaster CM754/939 (fan/heatsink), Thermalright heatspreaders + fan built on (RAM)
Memory 512mb PC-3200 DDR400 (set DDR-33 for o/c) by Corsair (matched pair, 2x256mb) 200.1/200mhz
Video Card(s) BFG GeForce 7900 GTX OC 512mb GDDR3 ram (o/c manually to 686 core/865 memory) - PhaseChange cooled
Storage Dual "Raptor X" 16mb 10krpm/RAID 0 Promise EX8350 x4 PCIe 128mb & Intel IO chip/CENATEK RocketDrive
Display(s) SONY 19" Trinitron MultiScan 400ps 1600x1200 75hz refresh 32-bit color
Case Antec Super-LanBoy (aluminum baby-tower w/ lower front & upper rear cooling exhaust fans)
Audio Device(s) RealTek AC97 onboard mobo stereo sound (Altec Lansing ACS-45 speakers - 10 yrs. still running!)
Power Supply Antec 500w ATX 2.0 "SmartPower" powersupply
Software Windows Server 2003 SP #1 fully patched, & massively tuned/tweaked to-the-max (plus latest drivers)
#16
I would deffintly go with a dual rail PSU, personly i think they are more stable.
On theory alone? Makes sense to myself as well...

By dedicating a 'rail' to the CPU for instance/example (I think that was noted above-earlier as what goes on in them regarding rails dedication), & the rest to the rest of the system? You are sort of "multitasking" & assuring power delivery imo!

BUT, again: I know "squat" about this area especially & live vicariously thru you guys on this account especially (power supplies).

Almost like SLI on vidcards &/or DualCore CPU + multiple thread designed code... which imo, makes GOOD sense for performance & yes, reliability (to a much tinier extent but there) in code running on CPU's!

APK
 

Tatty_One

Super Moderator
Staff member
Joined
Jan 18, 2006
Messages
19,823 (4.52/day)
Likes
6,102
Location
Worcestershire, UK
Processor Skylake Core i7 6700k @ 4.6gig
Motherboard MSI Z170A Tomahawk
Cooling Cooler Master Seidon 240V AIO/Viper140's
Memory 16GB Corsair Vengeance LPX 3000mhz CL14
Video Card(s) Sapphire 4gb R9 290X VaporX @1150mhz
Storage SkHynix SL308 120GB/CrucialM4/1TB WD Black
Display(s) LG 29inch 2560x1080 Curved Ultrawide IPS
Case Phanteks Enthoo Pro M Windowed - Gunmetal
Audio Device(s) Xifi Elite Pro 7.1/VideoLogic ZXR550's
Power Supply XFX Pro Black Edition 750W Gold modular
Keyboard CM Storm Octane Combo
Software Win 10 Home x64
#17
Thats interesting, I thought my was single as its 24a, but I guess not! :confused:
It can be confusing tho because some manufaturers refer to power ratings and they are actually quoting "peak power" which aint true power (usually the cheaper ones) mine is 24A True and 30 Amp peak (I think!), gonna check the manual now.:eek:
 

Tatty_One

Super Moderator
Staff member
Joined
Jan 18, 2006
Messages
19,823 (4.52/day)
Likes
6,102
Location
Worcestershire, UK
Processor Skylake Core i7 6700k @ 4.6gig
Motherboard MSI Z170A Tomahawk
Cooling Cooler Master Seidon 240V AIO/Viper140's
Memory 16GB Corsair Vengeance LPX 3000mhz CL14
Video Card(s) Sapphire 4gb R9 290X VaporX @1150mhz
Storage SkHynix SL308 120GB/CrucialM4/1TB WD Black
Display(s) LG 29inch 2560x1080 Curved Ultrawide IPS
Case Phanteks Enthoo Pro M Windowed - Gunmetal
Audio Device(s) Xifi Elite Pro 7.1/VideoLogic ZXR550's
Power Supply XFX Pro Black Edition 750W Gold modular
Keyboard CM Storm Octane Combo
Software Win 10 Home x64
#18
On theory alone? Makes sense to myself as well...

By dedicating a 'rail' to the CPU for instance/example (I think that was noted above-earlier as what goes on in them regarding rails dedication), & the rest to the rest of the system? You are sort of "multitasking" & assuring power delivery imo!

BUT, again: I know "squat" about this area especially & live vicariously thru you guys on this account especially (power supplies).

Almost like SLI on vidcards &/or DualCore CPU + multiple thread designed code... which imo, makes GOOD sense for performance & yes, reliability (to a much tinier extent but there) in code running on CPU's!

APK
Yes but wouldnt you find it frustrating if you blew the second rail because of overclocks on gfx card etc when you had loads of spare on the CPU 12V rail but couldnt use it. As I said in my first post, we all have our own opinions and bad experience with me personally steers me away from dual rails and after all, I have no stability issues on a single rail (the main reason why dual rail supporters prefer them) and look at my overclock. My current cheapish single rail has lasted me longer than the Tagan or Antec!
 
Joined
May 14, 2006
Messages
997 (0.23/day)
Likes
13
Location
Kentucky
System Name Sony Vaio - VGNFW390-CTO
Processor Intel® Core™ 2 Duo Processor T9550 (2.66GHz)
Cooling Stock
Memory 4GB DDR2-SDRAM (DDR2-800, 2GBx2)
Video Card(s) ATI Mobility Radeon™ HD 3650 with 512MB vRAM (pitiful card)
Storage 320GB SATA Hard Disk Drive [7200 rpm]
Display(s) LCD 16.4" (XBRITE-FullHD™)
Audio Device(s) SupremeFX
Software Windows 7
#19
I found an Ultra PSU that has a 12V rating of 40A. Here is the link. So far the reviews seem pretty good. Anyone with personal experience?

HTML:
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2341921&sku=ULT33183
 
Joined
Dec 6, 2005
Messages
9,941 (2.25/day)
Likes
3,894
Location
Manchester, NH
System Name Working on it ;)
Processor I7-4790K
Motherboard MSI Z97 U3 Plus
Cooling Be Quiet Pure Rock Air
Memory 16GB 4x4 G.Skill CAS9 2133 Sniper
Video Card(s) Power Color RD Vega 64 Reference
Storage Samsung EVO 500GB / 8 Different WDs / NAS with 2x2Tb WD Black
Display(s) 34" LG 34CB88-P 21:9 Curved UltraWide QHD (3440*1440)
Case Rosewill Challenger
Audio Device(s) Onboard + HD HDMI
Power Supply Corsair HX750 (love it)
Mouse Logitech G5
Keyboard Logitech G710 Blue / G610 Orion Red
Software Win 7 Pro
#20
Thats interesting, I thought my was single as its 24a, but I guess not! :confused:
Like Tatty said, when listed as 20A peak, 18A is the "normal" max.

The article explains that a 20A rail (*12v) provides a max of 240W (which is considered the "safe" limit for ATX power cabling - at 12v unless you cause a severe short probably won't hurt anyone, but components and connectors do indeed fail.).

This is all based on the ATX "standard"... which manufactures aren't obligated to follow - but should. Anyway, you may indeed have a 24A rail.
 
Joined
Dec 6, 2005
Messages
9,941 (2.25/day)
Likes
3,894
Location
Manchester, NH
System Name Working on it ;)
Processor I7-4790K
Motherboard MSI Z97 U3 Plus
Cooling Be Quiet Pure Rock Air
Memory 16GB 4x4 G.Skill CAS9 2133 Sniper
Video Card(s) Power Color RD Vega 64 Reference
Storage Samsung EVO 500GB / 8 Different WDs / NAS with 2x2Tb WD Black
Display(s) 34" LG 34CB88-P 21:9 Curved UltraWide QHD (3440*1440)
Case Rosewill Challenger
Audio Device(s) Onboard + HD HDMI
Power Supply Corsair HX750 (love it)
Mouse Logitech G5
Keyboard Logitech G710 Blue / G610 Orion Red
Software Win 7 Pro
#21
I found an Ultra PSU that has a 12V rating of 40A. Here is the link. So far the reviews seem pretty good. Anyone with personal experience?

HTML:
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2341921&sku=ULT33183
Yikes! They make "decent" units... I actually tried one of thier non-modular models when I thought my PSU was flaky. Even the 600W model is 35A on 12v rail... perhaps they don't break them out separately in the specs?
 

strick94u

New Member
Joined
May 24, 2006
Messages
1,592 (0.37/day)
Likes
70
Location
Texas
System Name CrashMaster 17.2/ crashmaster(M) ROG
Processor CD2 E8400@4.0 ghz/ i5 430@ 2.577 mhz
Motherboard EVGA 680i/ patogram inc intel north bridge
Cooling Monsoon vigor gaming II/ fan and vents
Memory 4 gig OCZ pc8500 DDR2/ 4 gigs ddr3
Video Card(s) 2 X EVGA 8800gts 512 735/1045/nvidia 360 gtsm gddr5
Storage 2 X WD 150 Raptors Raid 0+600gig usb/ 500 gig hitachi
Display(s) Samsung 2232 bw Sync Master 22" HD/16.9 inch asus
Case Enermax uber chakra/ asus republic of gamers
Audio Device(s) Creative SB X-FI 5.1 speakers/creative eax 4.0
Power Supply OCZ extream Gaming 650 watt 4x18a/ external
Software Dos 6.22/ win 3.11 for networks/ms bob server
Benchmark Scores 3dmark06 18,201/10601 3dmark05 23,943/not run Aquamark 218,094/not run
#22
I have 23 amps x 2 rails running sli without a hickup even if nvidia says 26 amps but in the thick of play with my fluke hookedup it never draws more than about 15 amps off the rails
but the sli connectors are on there own connectors how ever I clamp around every wire in the system
 
Joined
Oct 15, 2006
Messages
847 (0.21/day)
Likes
33
Location
St. Louis, MO
System Name QUAD1
Processor Intel Core i7 920
Motherboard Asus P6T SE
Cooling XIGMATEK HDT-S963
Memory OCZ 3 X 1GB Triple Channel
Video Card(s) HIS Radeon HD4670 IceQ
Storage Seagate 250GB 7200RPM SATA
Display(s) Acer AL1916W 19" Widescreen LCD
Case CM Storm Scout
Audio Device(s) Onboard
Power Supply Corsair 520 Watt
Software Windows XP Pro
#23
personally, when ever i build a computer, i make it a special thing to always have a dual (or more) rail psu. simply becouse it is newer technoalay (sp?).


chris
 

ghost101

New Member
Joined
Jun 3, 2006
Messages
1,328 (0.31/day)
Likes
164
Location
London
#24
X-bit labs have written a number of articles on PSUs. The most recent two are interesting reads.

http://www.xbitlabs.com/articles/other/

Especially this one which explains all the technologies.
http://redroad.wordpress.com/
http://www.xbitlabs.com/articles/other/display/atx-psu5.html

This what they have to say on dual rails.

In good old times PC power supplies used to have one power rail for each of the output voltages (+5V, +12V, +3.3V, and a couple of negative voltages), and the maximum output power on each of the rails was not higher than 150-200W. It’s only in some high-wattage server-oriented power supplies that the load on the +5V rail could be as high as 50A, i.e. 250W. This situation was changing as computers required ever more power and the distribution of power consumption among the different power rails was shifting towards +12V.

The ATX12V 1.3 standard recommends a max current of 18A for the +12V rail and this is where a problem occurred. It was about safety regulations rather than about increasing the current load further. According to the EN-60950 standard, the maximum output power on user-accessible connectors must not exceed 240VA. It is thought that higher output power may with a higher probability lead to various disasters like inflammation in case of a short circuit or hardware failure. Obviously, this output power is achieved on the +12V rail at a current of 20A while the PSU connectors are surely user-accessible.

So, when it became necessary to push the allowable current bar higher on the +12V rail, Intel Corporation, the developer of the ATX12V standard, decided to divide that power rail into multiple ones, with a current of 18A on each, the 2A difference being left as a small reserve. Purely out of safety considerations, there was no other reason for that solution. It means that the power supply does not necessarily have to have more than one +12V power rail. It is only required that an attempt to put a load higher than 18A on any of its 12V connectors would trigger off the overcurrent protection. That’s all. This simplest way to implement this is to install a few shunts into the PSU, each of which is responsible for a group of connectors. If there’s a current of over 18A on a shunt, the protection wakes up. As a result, the output power of none of the 12V connectors can exceed 18A*12V=216VA, but the combined power on the different 12V connectors can be higher than that number.

That’s why there are virtually no power supplies existing with two, three or four +12V power rails. Why should the engineer pack additional components into the already overcrowded PSU case when he can do with just a couple of shunts and a simple chip that will be controlling the voltage in them (the resistance of a shunt being a known value, the current passing through the shunt can be known if you know the voltage).

But the marketing folk just couldn’t pass by such an opportunity and now you can read on any PSU box that dual +12V output circuits help increase power and stability, the more so if there are not two but three such lines!

You think they stopped at that? Not at all. The latest trend is power supplies that have and don’t have the splitting of the +12V rail at the same time. How? It’s simple. If the current on any of the +12V output lines exceeds the 18A threshold, the overcurrent protection becomes disabled. As a result, they can still embellish the box with the magical text, “Triple 12V Rails for Unprecedented Power and Stability”, but can also add there some nonsense that the three rails are united into one when necessary. I call this nonsense because, as I have written above, there have never been separate +12V power rails. It’s impossible to comprehend the depth of that “new technology” from a technical standpoint. In fact, they try to present the lack of one technology as another technology.

As far as I know, the “self-disabling protection” is currently being promoted by Topower and Seasonic and, accordingly, by the companies that are selling such PSUs under their own brands
 
Last edited: