XPost: rec.electronics, sci.electronics, sci.electronics.basic   
   XPost: sci.electronics.basics, sci.electronics.equipment   
   From: CFKinsey@military.org.jp   
      
   Why do (cheap? expensive ones may be better) PC ATX power supplies need   
   current drawn from the 5V line to make the 12V line work correctly?   
      
   I have a PC with 3 graphics cards running scientific applications.  I acquired   
   three old graphics cards that take about 300W each, and have loads of cheap   
   (CIT) PSUs that are rated at 650W on the 12V line, which is what those cards   
   use.  So I run each    
   card off its own supply.  But the 12V line at no load, or even at 300W, is   
   only giving out 10 to 10.5V.  If I attach a small dummy load of an amp or so   
   to the 5V line, the 12V line suddenly becomes 12V.   
      
   Why are the two lines related in any way?   
      
   Sorry for the crosspost, I'm not sure which of these groups are active.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)