Dual rail? What?

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UlricT

Golden Member
Jul 21, 2002
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can some please explain the concept of dual 12V rail on a PSU? I have heard conflicting opinions as to whether this is good or bad. Some people say that there are timing issues with dual 12V rails. Other people say it is better....

I am talking specifically about the power supply of this case(Antec TX640B w/ 400W power supply). I have been having problems gettting it to work with this motherboard ( MSI K8N Neo4-F). I am getting erratic startups.

I was able to power the system up twice, but even a warm reboot would result in the machine not powering up again. This was with minimal components attached (cpu, vid, mem only). Any ideas as to why? I was thinking it is maybe because the timing of both the rails might be off or something (wild guess). Please look at this thread I created thinking that it was the lack of power that was causing this erratic behavior.
 
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UlricT

Golden Member
Jul 21, 2002
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thank you for the links... I wanted to specifically know how the power supply and motherboard work together. Any input in this matter would be really helpful.
 
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Zepper

Elite Member
May 1, 2001
18,998
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Dual rail/single rail it don't matter. What matters is that you have enough Amps available at 12V to cover the needs of your system (remember, you can only get the max rating of the 12V rails if the other rails are lightly loaded because they all work off the same primary winding in the transformer). The dual rail fad is mainly for safety (over 20A at 12V can be dangerous if you are in the habit of grabbing your PSU outputs while you are taking a bath... :roll: ). OTOH, split rails can cause a problem if one or the other isn't being loaded properly. You may need to adapt the rail that is being lightly used to help out the other which may be overloaded. That's why I recommend single +12V rail PSUs when possible.
. So you can check to be sure you have BOTH power leads connected to your mobo (the normal ATX one plus the P4, 4-pin square, plug) and if your video card requires an auxiliary power connection (could be on the card itself or on the mobo) , make sure it is connected too.
. It is also possible that your CPU overheated or you have the CPU fan connected to the wrong header on the mobo. On some mobos if the fan speed isn't detected properly on the CPU Fan (yes there is a specific one for the CPU fan) header the mobo will shut the system down for safety. So check that your heatsink is properly seated and that your CPU fan is connected to the CPUFAN header. Clear your CMOS exactly by the instructions in the manual and try again. Then report back.

.bh.
 
mechBgon

mechBgon

Super Moderator<br>Elite Member
Oct 31, 1999
30,699
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Zepper, there you go trying to discourage us from handling our PSU leads while we're in the bathtub again :p

;)

UlricT, if you have the case's front-USB cables plugged into the MSI's USB headers, unplug them as a fact-finding step. Some MSI motherboards are pinned out a little funky and have a +5V power pin where your case wiring might have a ground wire. My EPoX 8RDA+ was that way, took me some elimination to figure it out.

Also, if it were me, I'd think about an Antec SLK3000-B paired up with a heftier power supply. I ended up getting a TruePower 2.0 480W for my rig, which is spec'ed almost precisely like yours, and no issues yet. Although I haven't tried handling the power cables while taking a bath yet ;)
 
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Zepper

Elite Member
May 1, 2001
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Nah, that's just reverse psy... Hoping some may actually try it xx0x (lower case) . Judging from some of the posts lately, we desperately need to clean a lot of the stupid gene out of here! Here's your sign and it's conveniently made of metal and attached to a fully charged Ford coil...

.bh.
 
mechBgon

mechBgon

Super Moderator<br>Elite Member
Oct 31, 1999
30,699
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Originally posted by: Zepper
Nah, that's just reverse psy... Hoping some may actually try it xx0x (lower case) . Judging from some of the posts lately, we desperately need to clean a lot of the stupid gene out of here! Here's your sign and it's conveniently made of metal and attached to a fully charged Ford coil...

.bh.
Click to expand...
Sooo... that time when you told me to put the gasoline in the blender along with the handful of flinty rocks WASN'T an accident!!! :|





;)

 
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UlricT

Golden Member
Jul 21, 2002
1,966
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lol @ you guys... the system is at my friends place... will report back with what I have found. Everything was plugged in right though.... Took the whole thing apart and assembled it twice... will try disconnecting the front USB ports...
 
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fstime

Diamond Member
Jan 18, 2004
4,382
5
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Dual rail - Two water hoses watering a plant.

Single rail - one large hose feeding a plant.



There is nothing wrong with dual rail, it is just as good, if not better than single rail psus.

I myself went with the OCZ 600 PS 20A@12V1, 18A@12V2.



 
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Zepper

Elite Member
May 1, 2001
18,998
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Naah, dis sucka'll weigh ya down so ya cain't get out an weld ya ta da water spout... :shocked:

:shocked:

Zippy 950 !!!

:shocked:

This mama can possibly do over 60A (over 700 Watts) on ONE WIRE (12V2) before the short circuit protection kicks in - 70A total on both 12V rails (over 800W) typical see the chart near the bottom of the page!!!

.bh.
 
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