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Do I need to balance the rails to install my card?

Last response: in Graphics & Displays
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November 15, 2010 11:33:30 PM

I bought an XFX GT 240 card that I want to add to my Dell desktop computer.

It has a Bestec PSU are with two rails, one 12 amps and one 18 amps.

Do I need to do anything special other plug the card in? How do I found out which rail the CPU and the GPU are on, and is there any need to change that configuration?

I have a Quad Core Intel Q9400 process and three hard drives.

November 15, 2010 11:36:08 PM

usually the 24 pin MOBO connector will be on one rail (usually the 12 amp in this case) and the PCI-e plugs on the other so shouldn't need anything done to balance the load.
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November 15, 2010 11:55:04 PM

JDFan said:
usually the 24 pin MOBO connector will be on one rail (usually the 12 amp in this case) and the PCI-e plugs on the other so shouldn't need anything done to balance the load.


I looked at my system and there is in a 24-pin connector labeled "main power connector (ATX POWER)" and a 4-pin connector labeled "power for processor (ATX_CPU)".

JDFan, what does the 24 pin MOBO connector power?
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November 16, 2010 12:00:02 AM

It runs the MOBO itself and the MOBO slots (ie. the PCI-e slot provides up to 75W through each of the slots, the PCI slots also provide some +12v power, the fan connectors on the MOBO use a few watts each, etc.)

Really the only thing to watch is on the lines going to the video card do not use a splitter that also runs other components like the HDD, DVD drive etc. - since under load the video card can be pulling almost the capacity of those wires for the video card to use and if the HDD or DVD drive are siphoning off part of the capacity it can cause the system to be unstable.
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November 16, 2010 12:07:39 AM

Sorry to be dense, but you lost me there. From your first reply, I understood that the 24 pin MOBO and the PCI were on separate rails.
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November 16, 2010 12:09:36 AM

JDFan said:

Really the only thing to watch is on the lines going to the video card do not use a splitter that also runs other components like the HDD, DVD drive etc. - since under load the video card can be pulling almost the capacity of those wires for the video card to use and if the HDD or DVD drive are siphoning off part of the capacity it can cause the system to be unstable.


How do I determine whether the line to the video card is using a splitter? [As far as I know, the card does not use a separate plug; all of its power is from the PCI slot.]
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a b Î Nvidia
November 16, 2010 12:10:46 AM

the gfx card you have doesnt require that much power so I wouldnt worry about it too much. To find out what connectors run off what rail you really need to go to the PSU's manufactures website for a spec sheet, but bestec doesnt even have a website as they suck. sometimes its written on the side of the PSU. I would personally throw that PSU in the bin as Bestec are a rubbish brand that re-badges other rubbish brands and it will probably blow up. http://www.jonnyguru.com/modules.php?name=NDReviews&op=... Get yourself a decent PSU from a reputable manufacturer.
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November 16, 2010 12:15:22 AM

ratsa said:
Sorry to be dense, but you lost me there. From your first reply, I understood that the 24 pin MOBO and the PCI were on separate rails.


Sorry for the confusion -- the slots on the MOBO are powered by the 24 pin MOBO connector -- the auxillary connectors for the PCI-e card are seperate ( the 6 or 8 pin PCI-e connectors).

for a video card the PCI-e slot itself can provide up to 75W of +12v power without an auxillary connector if the card uses more than 75W then the video card will need a 6 pin or 8 pin power connection to the PSU ( 6 pin can provide 75W more and 8 pin up to 150W)-- so say you have a 5770 GPU which can use 108W it would use up to 75W from the MOBO connector and then need a 6 pin connnection to provide the excess -- IF you have even a higher usage GPU then if it uses over 150W it would require 2 6-pin connections for up to 225W (75+75+75) or a 6-pin and an 8-pin if it might use more than 225W under load (ie. the nvidia 480 )
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November 16, 2010 12:18:48 AM

ratsa said:
How do I determine whether the line to the video card is using a splitter? [As far as I know, the card does not use a separate plug; all of its power is from the PCI slot.]


Normally nowadays it will use a 6 or 8 pin connector so no need to worry unless you are using a MOLEX to 6-pin adapter in which case just make sure the molex connection from the PSU is not split off to run the HDD or DVD drive -- so it should come straight from the PSU to the video card (if the wire splits into 2 connections on the end then only use the 1 end and leave the 2nd connection withoout anything attached)

EDIT : Just looked and your card does not need an auxillary connection so no need to worry since it will pull all of it's power from the PCI-e slot (was not sure on the Nvidia card if the 240 was that low of power usage !)
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November 16, 2010 12:19:54 AM

The GT 240 uses 70 watts max, which it can draw directly fro the MOBO.

If I understand correctly, that means the CPU will have the 18 amp rail all to itself and the video card along with hard drives, fan etc. will use the other 12 amp rail?
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November 16, 2010 12:23:48 AM

JDFan said:
Normally nowadays it will use a 6 or 8 pin connector so no need to worry unless you are using a MOLEX to 6-pin adapter in which case just make sure the molex connection from the PSU is not split off to run the HDD or DVD drive -- so it should come straight from the PSU to the video card (if the wire splits into 2 connections on the end then only use the 1 end and leave the 2nd connection withoout anything attached)



The card hasn't arrived, but I didn't think it had a connector at all. At least it wasn't mentioned anywhere on either XFX or nVidia websites. I could be wrong about that though.
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November 16, 2010 12:24:54 AM

ratsa said:
The card hasn't arrived, but I didn't think it had a connector at all. At least it wasn't mentioned anywhere on either XFX or nVidia websites. I could be wrong about that though.


Yes the 240 is a very low power consumption card so does not use an aux connection so you'll be fine !! (wasn't sure what the 240 needed but just looked over at newegg !)
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November 16, 2010 2:26:08 AM

some of those bestec psu's are notorious for being cheap and destroying computers.
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November 16, 2010 10:40:39 AM

rand_79 said:
some of those bestec psu's are notorious for being cheap and destroying computers.



Even the ones used by Dell? I thought Dell's psu specs were conservative.
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