The Dual Rail v. Single Rail Challenge

[Algere]

Originally posted by: Zebo

Originally posted by: DocQ
Excellent posts. I just bought a Enermax EG375 (370W) dual +12v rail PSU. Plenty of juice on the +3.3v (30A) and the +5v (32A)... but I'm questioning the +12v rails. 12v1 (14A) and 12v2 (13A). Here's why: just put in a MSI GeForce 6600GT AGP card (replaced my nVidia MX400). System runs perfect in windows... and in 2D.. Even COD runs flawless; however, when I run 3DMark01/03/05, video freezes and system locks up.. it doesn't reboot though. I started disconnecting +12v components until I only had my boot HD and 6600GT powered.. still froze. My question is: does the AGP slot power off the same +12v rail as the CPU... or the other 12v rail (HD/opticals/etc) ? I used a dedicated molex called "Extra" to power the 6600GT.. but not sure which rail it hits?
Started getting message (from nVidia control panel) "video card cannot draw enough power.. adjusting...."

Athlon XP 3200+
ASUS A7N8X-LA nForce2 400 chipset
MSI 6600GT AGP 128
200Gb Maxtor HD
160Gb Samsung HD
ASUS 16x DVD-ROM
RICOH MP5240A DVD+RW
Floppy / 4 in 1 flash media readers / 6 USBs / 1394 ports
Enermax EG375P-VE SFMA 370W PSU

Replies greatly appreciated....

It's about 50/50 power draw. The plug you plug in to card is the second rail.

Rail 1: is both mobo connectors (20/24 pin and P4/or 8 pin)
Rail 2: is all molex/floppy connectors

You problem is rail 1IMO.. but why guess? get a fat single 12.

Rail 1 or 2 is just the 4-pin CPU plug only, on that PSU model.

OP: If the A7N8X-LA is similar in design to the A7N8X Deluxe in that there isn't a 4-pin CPU power connection on the motherboard, rail 1 or 2 is technically unused. In that case, your system is pretty much running off of one +12V rail in total. To make matters possibly worse, that Enermax model (old) could choke and/or shutdown @ full load according to SilentPCReview & TrustedReviews. Therefore there's a possibility you have even less than 13 or 14A altogether.

Sorry

 

[FastEddie]

Originally posted by: DocQ
Excellent posts. I just bought a Enermax EG375 (370W) dual +12v rail PSU. Plenty of juice on the +3.3v (30A) and the +5v (32A)... but I'm questioning the +12v rails. 12v1 (14A) and 12v2 (13A). Here's why: just put in a MSI GeForce 6600GT AGP card (replaced my nVidia MX400). System runs perfect in windows... and in 2D.. Even COD runs flawless; however, when I run 3DMark01/03/05, video freezes and system locks up.. it doesn't reboot though. I started disconnecting +12v components until I only had my boot HD and 6600GT powered.. still froze. My question is: does the AGP slot power off the same +12v rail as the CPU... or the other 12v rail (HD/opticals/etc) ? I used a dedicated molex called "Extra" to power the 6600GT.. but not sure which rail it hits?
Started getting message (from nVidia control panel) "video card cannot draw enough power.. adjusting...."

Athlon XP 3200+
ASUS A7N8X-LA nForce2 400 chipset
MSI 6600GT AGP 128
200Gb Maxtor HD
160Gb Samsung HD
ASUS 16x DVD-ROM
RICOH MP5240A DVD+RW
Floppy / 4 in 1 flash media readers / 6 USBs / 1394 ports
Enermax EG375P-VE SFMA 370W PSU

Replies greatly appreciated....

The square 4-pin AUX 12v connector for the cpu is one of the 12v rails, and the main atx connector paired with all the drive power connectors is the other 12v rail.

 

[DocQ]

"... Rail 1 or 2 is just the 4-pin CPU plug only, on that PSU model..."

"....The square 4-pin AUX 12v connector for the cpu is one of the 12v rails, and the main atx connector paired with all the drive power connectors is the other 12v rail...."

Thanks for the input. My Mobo (A7N8X-LA) does NOT have any power input connectors on the board (other than the 20pin ATX main connector). According to the specs, Enermax says that one rail powers the Motherboard (which is the ATX connector) and CPU.. while the other rail powers the drives. So the Mobo should be on a separate rail from drives. Also, since I can't plug in my AUX 12v connector, the CPU must be getting it's juice from the Mobo connection and rail, correct?

If, as you state, the ATX connector AND ALL the Molex connectors draw off of one rail...then my entire system is trying to survive off of rail-1 (14A) or rail-2 (13A)l

By my estimates, here's my +12v AMP draw:

AthlonXP 3200+ (75W / 12v = 6A)
6600GT AGP (3 to 4A)
Mobo (2 to 3A)
HDD1 (1 to 2A)
HDD2 (1 to 2A) (disconnected during test)
DVD1 (1 to 2A) (disconnected during test)
DVD2 (1 to 2A) (disconnected during test)
-------------------------------------------------
Total: 12 to 15A (just using 6600Gt and boot disk)

Are these correct assumptions?

 

[Algere]

According to the specs, Enermax says that one rail powers the Motherboard (which is the ATX connector) and CPU.. while the other rail powers the drives.

Are those specs from the PSU's manual & specifically listed under your PSU's model? Not all two rail Enermax PSU models have the same configuration. AFAIK there's this configuration (below). Found on older and/or lower powered PSU models.

One rail = 4-pin CPU (2x2)
Other rail = 20/24-pin main, floppy & 4-pin molex, etc.


Then there's this configuration which can be found on the newer & higher rated models.

One rail = 4-pin CPU (2x2), 20/24-pin main, SATA
Other rail = floppy & 4-pin molex, & video card power

Also, since I can't plug in my AUX 12v connector, the CPU must be getting it's juice from the Mobo connection and rail, correct?

Rail -> MB -> CPU & correct, CPU gets it's power from the 20-pin main connector.

If, as you state, the ATX connector AND ALL the Molex connectors draw off of one rail...then my entire system is trying to survive off of rail-1 (14A) or rail-2 (13A)l

You got it :thumbsup: unless PSU manual says different.

By my estimates, here's my +12v AMP draw:

AthlonXP 3200+ (75W / 12v = 6A)
6600GT AGP (3 to 4A)
Mobo (2 to 3A)
HDD1 (1 to 2A)
HDD2 (1 to 2A) (disconnected during test)
DVD1 (1 to 2A) (disconnected during test)
DVD2 (1 to 2A) (disconnected during test)
-------------------------------------------------
Total: 12 to 15A (just using 6600Gt and boot disk)

Are these correct assumptions?

Were fans powered too? IIRC the Athlon XP gets some if not all of its power from 5V. If there is 12V consumption from the AXP, I doubt (not sure) there's 6A of it. As for the other components, assuming these figures are close, that should give you an idea of the amount of power being consumed.


P.S. Also contact Enermax, there could be a chance your PSU isn't delivering all the power it's spec'd for (defective).

Update: Apparently I didn't iiRC about the source of power the AXP consumes from. According to FiringSquad, the Athlon XP receives all of it's power from 12V. In addition, the 6A estimate may be a little on the low side - albeit close.

 

[FastEddie]

With onboard sound, onboard lan, it's better to give the motherboard a 7a rating for it's draw in figuring power consumption, where the Northbridge is going to consume most of those amps.

This very scenario is the reason why multi-rail psu's suck. They can't deliver enough power to the given rail.

 

[Zebo]

This very scenario is the reason why multi-rail psu's suck. They can't deliver enough power to the given rail.

------

Yup. Really true when OCing. I've tried it with dismal results. My comp would shut down when running games.. not really 100% shut down though.. hard drives still spun and comp light was still on.. but total black screen.. Pretty scary IMO.

 

[maluckey]

The deal with true dual rails is not for extra current, but for isolation and stability, and capabilities really depend on the specifications (EPS +12v, ATX-GES etc..) for the PSU. Some are designed for Dual CPU setups and/or servers. Strangely enough, servers are usally more concerned with noise isolation and stability, than ratings and raw current. don't get yourself lost in the wattage/amperage game. Look for Mean current of ALL rails under load at once (not just one rail as many companies test) at 50c. and you will be fine. That's the reason why FSP units seem so good for so little. They measure at 50c. for the high-end units, and all rails are under load during the test. Pre-burned and certified......Just from a simple test, you cannot tell how much in reserve that you have with any given PSU. You COULD be at failure and not know it. That's why I discount ANY PSU test that does not go to failure with all rails loaded to at least max ratings. Sure, this test may kill a lesser PSU, but the better designed should shut down to protect themselves.

This being said, any PSU without protection built in should not be considered at all. Replacing Motherboard, CPU, RAM and drives due to PSU failure is EXPENSIVE.

Back to the Dual Channel controversy...

Find me a PSU that can hold versus the FSP550 (ATX GES), for under 80 bucks and I'll buy it today. I can't find one in the same class for that price..........can anyone else???

 

[DocQ]

PSU question: What voltage draw is considered "out of range" from a PSU on each of the +12v, +5v, and +3.3v lines? Using a multimeter, I just ran a few tests at system ide.. and at load (runing 3DMark01 and 3DMark03). Here are my measurements:
+12v @ Idle = 12.33
+12v @ Load = 12.42 to 12.45
+5v @ Idle = 5.13
+5v @ Load = 5.08 to 5.10
+3.3v @ Idle = 3.378
+3.3v @ Load = 3.386 to 3.389

Is 12.33 (and 12.45) considered "to high" on the +12v line? (and cause instability and possible video freeze?)

PSU is an Enermax dual rail +12 EG375P-VE-SFMA

 

[Algere]

It's fine, not great. You're in the green as long as it doesn't exceed 12.6V.

 

[sechs]

I'm not sure that we've really learned anything from jdogg707's experiment -- especially since he didn't measure both +12v rails on the Enermax.

 

[FastEddie]

Originally posted by: sechs
I'm not sure that we've really learned anything from jdogg707's experiment -- especially since he didn't measure both +12v rails on the Enermax.

What would be the point? If one of the 12v rails is maxed to the extreme, why would knowing what the other 12v rail was pulling do for the equation? It's not like you can turn one rail down and the other rail up.

 

[Wall7486]

Dual Rail PSUs seem to be fine. I have the Enermax Noisetaker 600W. My rig is the following:
Asus A8N-SLI Deluxe
Athlon64 AMD 4000+
Zalman 7000B Cu
2x eVGA 6800 GT
Crucial DDR500 1GB
74GB WD raptor hard drive
NEC 3520

It is as stable as it can get. There were no issues or what so ever. I've got the rig for about a week already and it has yet to freeze or lock up in games.

 

[FastEddie]

Originally posted by: Wall7486
Dual Rail PSUs seem to be fine. I have the Enermax Noisetaker 600W. My rig is the following:
Asus A8N-SLI Deluxe
Athlon64 AMD 4000+
Zalman 7000B Cu
2x eVGA 6800 GT
Crucial DDR500 1GB
74GB WD raptor hard drive
NEC 3520

It is as stable as it can get. There were no issues or what so ever. I've got the rig for about a week already and it has yet to freeze or lock up in games.

Done any overclocking yet?

 

[Ctrl Z]

Looks like this Enermax EG465P-VE FMA 1.3 might be exactly what I'm looking for. But can you confirm it has a 24 pin motherboard connector? Because while I've seen references that appear to indicate this, I've also seen it described as having a 20 pin main power connector such as at the Enermax site: http://www.maxpoint.com/products/pow_supp/spec_pg/whisper2/

 

[sechs]

Originally posted by: FastEddie
What would be the point? If one of the 12v rails is maxed to the extreme, why would knowing what the other 12v rail was pulling do for the equation?

So one rail is being used. What does that prove?

 

[FastEddie]

The point I've trying to make for months is that when one of the 12v rails of a dual rail psu gets maxed out---as in working at or near 100% of it's capacity, 100% of the time---it really doesn't matter how much current or output is available on the second rail because the maxed rail has no way of utilizing that seperate output.

 

[maluckey]

But you have to remember that if you buy the dual rail unit with forethought about the load you will use on the CPU rail, you will be just fine. I don't know of many people, including using Water Cooling/TEC setups that have over 35a of +12v total current draw. On the same note, how many people actually can push 16 amps worth of HDD cooling fans etc? The dual rail merely splits the duties of the +12v between the CPU and I/O for isolation. That's all. If the board is setup for dual rail, you will not see a difference other than improved stability, by using the dual +12v PSU. If you try to split the +12v rail from a single rail, there have been tests showing instabilities, regardless of the +12v line amperage.

Single +12v rail PSU's will go the way of AT PSU's in a very short while, so getting used to the ATX-GES and EPS-+12v would be a good thing.

Here is an example of a certain ATX-GES PSU, rated with all rails under max load at 50C. Note the almost 32a of current still available on the +12v. Try to overload this 50-70 dollar PSU.....I dare you......

+3.3v = 27a
+5.0v = 29a
+12v = 16.5a (CPU )
+12v = 15.0a (I/O)

 

[Slaimus]

Unfortunately, those are all max load numbers. A 16amp max load 12V rail can only output about 10amps continuous.

 

[maluckey]

Not quite,

This is listed as not peak output, but maximom load that it is rated for at 50C. What you have is 16.0 amps to the CPU. You will have no guarantee of stability at over 16 amps though.

You can bet that it will put out more current than advertised every time.

The only time that I could get it to shut down was when I grounded out the +12v line to the case by mistake. It cooled off and was fine though.

 

[DSYee]

But as I understand it, even disregarding the fact that no single 12V rail can put out more than 16.5a (max), you can't just add 16.5 + 15 and assume you'll get 31.5a if you max out both rails. Most PSUs seem to have a cap on total 12V current that is less than the sum of the max output of both rails, e.g. 12V1 @ 18a, 12V2 @ 14a, total 12V @ 29a. Some manufacturers list this in their specs, but it seems a lot of others don't...

 

[dheffer]

I'm looking at getting an enermax psu, with 14V on one rail and 13V on the other... I was told that my system needs about 18V to run well (A64 2.4ghz, 1gb ram, 6800gt, 1 hard drive, 1 optical drive)... so how would that work out?
Would this be enough for what I have? Thanks!

 

[FastEddie]

Originally posted by: dheffer
I'm looking at getting an enermax psu, with 14V on one rail and 13V on the other... I was told that my system needs about 18V to run well (A64 2.4ghz, 1gb ram, 6800gt, 1 hard drive, 1 optical drive)... so how would that work out?
Would this be enough for what I have? Thanks!

Have you been asleep through this entire debate? 14a on one rail and 13a on the other 12v rail won't do at all---not even close to supplying adequate power for a stock Sli system, let alone one with dual graphics and a higher rated A64.

 

[dheffer]

Well, I didn't mean SLI... I guess I just didn't see a definitive answer... I've asked this same question on SPCR and they said that it would be enough

 

[FastEddie]

Save your money and pick up this one---> Athena Power 500W I've used it in all my Sli builds, including FX55/Dual 6800Ultra's. This unit comes highly recommended by Tyan in server/dually environments, which are going to give it alot more stress than a Sli box will. It's an excellent unit at three times what Newegg is charging for it.

 

[dheffer]

Hey,
I really don't think I need that much power, but I have heard some good things about Athena Power.
I'd also like to have a quieter PSU, like a seasonic or an enermax