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Question regarding routing power from my PSU to my Sapphire HD 7970 - Page 4

post #31 of 34
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Quote:
Originally Posted by WOD35 View Post


I may be wrong but sounds like his 8 pin PCI-E is actually 6+2, so he didn't use a 6 pin to 6+2 adapter, he just used the 6+2 PCI-E and replaced the 6 pin PCI-E with dual molex to 8 pin PCI-E.

The question I have about this setup is, how sure are you the molex connectors aren't on the same rail as the 6+2 PCI-E? Using the 6 pin PCI-E with 6 to 6+2 adapter assures you that that plug is drawing from the 2nd rail. It would make most sense for the manufacturer to put molex +12V on the rail with the smaller PCI-E connector though, so it's probably the same

You are correct, what I called an 8 pin connector is really a 6+2 pin, which I just assumed could be called the same thing. As for your question, I have no idea if the molex connectors are on the same rail as the PCI-E, and I'm not really sure what "rail" means in this context honestly...
post #32 of 34
Well the main things to pay attention to as far as PSU's for GPU's is the number of +12V rails, and the number of amps per rail. Wattage talk is mostly marketing garbage.

If you have 2 550w psu's, one with a single 40 amp rail and 1 with 2 20 amp rails, you would need to be sure to power a 23a card from 2 connections from separate rails, but on the single rail psu it wouldn't matter.

Since you have two +12v rails @ 24a each, and you have 2 PCI-E connectors that are for sure on seperate rails, but one is 6+2 pin and the other is 6 pin, it's almost certain that the molex get their power from the same rail as the 6 pin PCI-E as it would be expected to see less draw and therefore have more to share than the rail with the 6+2 pin PCI-E on it
post #33 of 34
It seems I was wrong about the 2 PCI-E being on seperate rails. According to Johnnyguru...
http://www.jonnyguru.com/forums/showthread.php?t=3990


Typical multiple +12V rail configurations:
2 x 12V rails
Original ATX12V specification's division of +12V rails.
One rail to the CPU, one rail to everything else.
VERY old school since it's very likely that "everything else" may include a graphics card that requires a PCIe connector.
Typically only seen on PSU's < 600W.

So it seems both PCI-E are on the same 24a rail. Which makes sense for a 22a card and you being just slightly above the recommended PSU wattage for the card. So it seems it doesn't matter how you hook it up. Even a 6 pin to dual 6+2 pin adapter would be fine as long as you stayed under your rail amps rating and didn't try to power a second or larger card with the other PCI-E

and this is taken from the toms hardware link I posted a couple pages back


Even though the specification allows for a delivery capability of 75 W (six-pin connector) or 150 W (eight-pin connector), the total power-handling capacity of these connectors is at least 192 and 288 W, respectively, using standard terminals, and even more using the HCS or Plus HCS terminals.
Edited by WOD35 - 8/22/13 at 7:18pm
post #34 of 34
nice one WOD35... its useful info you posted thumb.gif
my budget gaming
(10 items)
 
   
CPUMotherboardGraphicsRAM
i5 4570 Asus Z87-m Plus Zotac GTX 750 ti OC 8gb (4gb x 2) Samsung DDR3 1333 LV 
Hard DriveHard DriveCoolingOS
Western Digital 1tb Seagate 2tb stock Windows 8.1 Pro 
MonitorCase
HP Elitedisplay E231 abko ncore s2 mini tower 
CPUMotherboardGraphicsGraphics
i7 4770k Gigabyte G1 Sniper 5 XFX r9 290 XFX R9 290X BF4 Edition 
GraphicsGraphicsRAMHard Drive
Power color R9 290 Sapphire R9 290X BF4 Edition G.Skill Trident X 2666 mhz CL12 Samsung 840 EVO 250gb 
Optical DriveCoolingOSMonitor
Samsung DVD writer Custom Water cooling WIndows 8.1 Professional Crossover 3020MDP 
MonitorMonitorKeyboardPower
Crossover 30X-P  Crossover 30X-p Steel Series 6Gv2 Mechanical Keyboard with Cher... Corsair ax1500i 
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Corsair 900D Logitech G100 Creative 3d Core (stock G1 Sniper 5) Corsair Vengeance 1400 Analog Gaming Headset 
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my budget gaming
(10 items)
 
   
CPUMotherboardGraphicsRAM
i5 4570 Asus Z87-m Plus Zotac GTX 750 ti OC 8gb (4gb x 2) Samsung DDR3 1333 LV 
Hard DriveHard DriveCoolingOS
Western Digital 1tb Seagate 2tb stock Windows 8.1 Pro 
MonitorCase
HP Elitedisplay E231 abko ncore s2 mini tower 
CPUMotherboardGraphicsGraphics
i7 4770k Gigabyte G1 Sniper 5 XFX r9 290 XFX R9 290X BF4 Edition 
GraphicsGraphicsRAMHard Drive
Power color R9 290 Sapphire R9 290X BF4 Edition G.Skill Trident X 2666 mhz CL12 Samsung 840 EVO 250gb 
Optical DriveCoolingOSMonitor
Samsung DVD writer Custom Water cooling WIndows 8.1 Professional Crossover 3020MDP 
MonitorMonitorKeyboardPower
Crossover 30X-P  Crossover 30X-p Steel Series 6Gv2 Mechanical Keyboard with Cher... Corsair ax1500i 
CaseMouseAudioOther
Corsair 900D Logitech G100 Creative 3d Core (stock G1 Sniper 5) Corsair Vengeance 1400 Analog Gaming Headset 
  hide details  
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