Psu 8 pin port faulty? Picky psu regarding cables?

[roland.blomqvist]

Setup:
Fx-8320
M5a99x pro evo 2.0
Evga gtx 660
12 gb ddr3
Coolermaster real power m850 (rs-850-esba) modular power supply for 850w

Ive run this setup with everything flawlessly. The gpu uses a 6 pin to 6 pin pcie connector to the psu.

Now I wanted to put in a asus gtx 770 which requires a 6pin + 8pin pcie power setup.

Problem is, when I try to boot with these connected. The fans go on and off and nothing happens.

The 770 has been tried in other pcs. Fully functional.

The setup boots up with no power connected to the gpu, and with only 6pin connects. But can't naturally get past the boot menu ofcourse.

I've tried switching back to the gtx 660 and using the 8 pin to 6+2 cable and plug it from the psu 8 pin to the gpu 6 pin. Same problem. I've tried several different 8 pin cables and when any of them are connected the same problem occurs. Fans on and off again, no response. All lights are green.

To me it seems that the psus 8pin port is either faulty or it requires only the original cable that came with the psu purchase, which I currently don't have anymore.

What do you guys think? Is this psu so picky with its cables that only originals work?

Thanks in advance for all the help I can get // R

 

[jay32267]

I'd tend to lean more towards a faulty port than the cables.

Regardless....check the voltages at the graphics card end with the cable hooked to the PSU. See below.


Pinout
Pins 1 through 3 Pins 4 through 6
Description Wire color Pin number Pin number Wire color Description
+12 volts yellow 1 5 black ground
+12 volts yellow 2 6 black ground
+12 volts yellow 3 7 black ground
ground black 4 8 black ground

Pins 1-3 are 12V
Pins 5-8 are ground

 

[zyh1987]

with modular supply, not all company uses the same layout at the psu side, the output of your cable is standardized. not the input side.
you would need the original cable, or cable with a matching pin out. otherwise you are at very high risk of messing up your graphic card!
you can get the cable from some aftermarket modding company or CM.

i hope you did not destroy your card by doing so.

you can also test the outputside voltage using a voltage meter (change the mode to dc, if it doesnt have auto selection, change your range to 2V-20V)

http://www.hardwarecanucks.com/forum/power-supplies/72260-so-how-would-someone-get-power-pci-8pin.html

output should be like this. yellow and back should give you 12V or very close to 12V. if you dont have these reading,

i don't have the exact pinout for the psu side, see if you have correct pcie 8 pin voltage first, then we can help you troubleshoot a bit more.

good luck.

 

[DSzymborski]

Yup, as zyh notes, modular PSU cables are not interchangeable in this manner. There's a very real risk you've damaged your GPU by using a cable meant for one specific pinout with another.

 

[roland.blomqvist]

Gpu still working fine through benchmarks in other machines. Regarding cable layout, they're all the same 3 12v and 5 grounds. Same plug shapes for all. Nothing works in 8pin. I put in a different psu now, non modular and it all works now well. Still wondering about the original psu why it didn't work.

 

[zyh1987]

You can use a voltage meter to find out the voltage. At the input and output side. Are you getting any actual voltage at output side? If yes, do they conform to the pcie standards pinout? If you are not getting any voltage, psu is likely the issue. If your voltage output doesn’t match pcie 8pin standards. Cable is likely the issue. Compare the actual reading, not the color code.