The significance of dual 12v rails

[Pythias]

The hows and whys of dual 12v rails

 

[ZL1]

Good read
Thank you for the link man

D

 

[orangat]

Finally someone who knows what he is talking about and this should strip the myth that dual rails are somehow more stable and better.

The prevailing myth is that dual rails is cheaper to build and a better design when it is more costly and inefficient.

 

[GalvanizedYankee]

Thank you OP for the good read. This may add to your links info, on the bottom of page 3
Edward Chang of Zippy comments on dual +12. A highlighted comment on the bottom
of page 2 is worth reading. It concerns the adding of fans inside an ATX spec box.

I have seen quad rail PSUs being marketed(chosen word )


Galvanized

 

[MaxisOne]

Damn goood read ... prolly explains why my rig performs sub par unless i plug out 2 of my hard drives

running
Athlon 64 3800
1 sata raid stripe= 2 Sata Drives
2 IDE Drives
2 CD/DVD drives
SB Audigy
ATI X850 XT PE
Under a NEOPower 480

 

[suszterpatt]

Interesting read, thanks.

 

[Zepper]

Time for a little "superiority dance" here!

I've said that this dual rail thing has been a fad and strictly safety oriented with no other redeeming value - apparently Intel agrees, as per the OP's linked article they aren't even sticking to their own spec. I've recommended single rail PSUs like the Sparkle FSP550-60PLG and Zippys all along. Single rail will always be more flexible and only a danger to those who insist on grabbing their PSU's 12V leads while taking a bath. :roll:

.bh.

Here, have a :beer: !

 

[maluckey]

Unless you want a DFI NF4 Ultra SLi. DFI states time and again to ONLY use native 24pin solution for these boards. It's even on the support page...

 

[Suspicious-Teach8788]

Well this doesnt indicate anywhere how my 600W Seasonic with 18A per rail is a piece of crap.

 

[Zepper]

DLe...
600W Seasonic is not a piece of crap - Seasonic just got sucked in by Intel's spec. But it won't be very useful if you find you need MORE than 18A on a given rail on occasion... With a single rail, your load could "borrow" a few extra Amps on occasion. Engineers should stick to what they know is best - even against giants like Intel. "Question Authority" - a useful adage to remember regardless of the field you play in.

mal...
Where does it say that a single rail PSU can't have 24-pin EATX (extended ATX, now called EPS12V) connector. They had them for a long time prior to the split rail fad...

.bh.

 

[BonzaiDuck]

I could be "in over my head" here, but I've concluded an 18A rail is anemic. It's probably adequate for a simple system with mainstream processors. I have a couple of them. But every time I have voltage drops that seem to derive from modest though respectable over-clocking, it was with a PSU with minimum 12V amperage.

Thanks for debunking the myth.

 

[orangat]

From the article it look like most dual rail ps are actually single rail in the guts anyway but cap the max. output. So there is no actual stability improvements.
In any case dual rails make the ps less flexible for future power needs especially for Intel CPUs.

 

[furballi]

A well-designed PSU from a reputable mfr will power the CPU and MB using one rail, with the video card and other accessories on the other rail. The CPU/MB rail should deliver at least 16A, and the combined 12V rails should have a CONTINUOUS rating of at least 28A. Pay attention to the efficiency number. Heat is the number one reason why the PSU fails to deliver the maximum output current. Make sure that the case is well vented and that the PSU is rated at 75% efficiency.

It is VERY rare for a system to drive all the components at 100% load. Therefore 350 watts of clean power is more than adequate for all but the most exotic system.

Here's one specific example:

AMD 3000 Venice overclocked to 3800 speed with 1GB RAM, 160GB 7200 rpm HDD, USR 5610B hardware modem, wireless PCI network card, DVD burner, Zalman 7700Cu CPU cooler, floppy drive, and two 120x38mm medium speed Panaflo fans. When all devices are running at full speed, the actual maximum load is approximately 220 watts. Prime95's max heat uses the most juice from the CPU.

 

[svi]

I've said that this dual rail thing has been a fad and strictly safety oriented with no other redeeming value

Well, from the seller's standpoint, the fact that they can jack up the price of dual-rail PSUs a little due to their popularity definitely qualifies as a redeeming value. We should be thankful that these sellers and manufacturers give us the opportunity to widen their profit margins; we live in a global marketplace, and every bit we do will help make the global economy that much healthier.

I could be "in over my head" here, but I've concluded an 18A rail is anemic. It's probably adequate for a simple system with mainstream processors. I have a couple of them. But every time I have voltage drops that seem to derive from modest though respectable over-clocking, it was with a PSU with minimum 12V amperage.

No offense meant, but you are off a little here. First off, DLeRium said 18A per rail, implying multiple rails; secondly, 18A on a single +12V is still plenty for most systems provided that the PSU is rated adequately. A high-end A64 with a 7800GTX will draw no more than 200W from the PSU (<250W from the wall, if you want to check this out with tests that measure power consumption at the wall socket) under heavy load.

There is always a difference between loaded voltage and unloaded voltage with any real-world power supply, especially with the relatively crappy (in terms of voltage regulation) PSUs PCs use. While it is true that rail amperage and voltage regulation are correlated (albeit not to any great degree), poor voltage regulation does not imply that the rail is being overloaded; rather, it is that PSUs with lower ratings are more likely to be budget-grade parts with cheaper, poorer-performing components / design.

 

[JEDIYoda]

I have always argued against those that said dual rails were far superior to single 12v rails!!!

 

[maluckey]

It's that in theory they should split the duty up between two totally separate +12V rails. In practice it's not always done well. If done right, you can use smaller, cheaper and cooler running transistors etc. (which means quieter fans). If done right, multiple rails can isolate cross-talking noises like from neon lighting, HDDs and fans and other misc.

In theory it's great, but in practice it's not always the same.

 

[ElTorrente]

lol if you have a Seasonic S-12 dual rail, you are fine.. don't throw your PSU away because dual rails are supposedly "inferior". Your components will get plenty of power reliably and you don't need to worry about it.

 

[raildogg]

OCZ Powerstream 520W FTW!

 

[TraumaRN]

Hmm this is probably why I ordered this power supply because it has the combine rail switch...so essentially the 2 12V rails become one...

 

[sandeep108]

So in effect I need not worry that my Antec TP480 with a 20>24 adapter is in anyway 'inferior' to a dual rail PSU for my A8N-E? In fact it ran quite ok even without the adapter. I was not too sure but a PC tech I knew said he knew several systems running just fine with that PSU and not to bother upgrading.

 

[furballi]

Adapter is bad because it adds contact resistance. A 0.05 ohm contact resistance will result in a drop of 0.5 volt at 10A.

 

[Zepper]

Yes, a POX on adapters/extensions in high current circuits!

.bh.

 

[coomar]

so my psu only supplies 18A on the 12V line?

and its not on nvidia's sli list

 

[maluckey]

Ummmm, no. It says on your link that it supplies 36 amps over two 12 volt lines. +12v1-18 am and +12v2-18 amps.

It may not have been tested, and that could be the reason it is not on the list.

 

[t3h l337 n3wb]

Yeah, my next PSU is definitely going to be the 550W Sparkle monster. About the same cost of a TruePower II, but much better.