PSU Cables output question.

[le modulor]

Power Supply Cables output question. I have a Gigabyte Superb E720 PSU with four 12V rails each with an output of 18Amps. Would I get more Amps if I use a "2x Molex to 6-Pin" adapter instead of one of the two 6-Pin cables available on my PSU. Also, can someone pls confirm the power outputs of 1) 6-Pin, is it 75W?, 2) 8-Pin, is it 150W?, 3) Molex, is it 132W? also, shouldn't these power output ratings be dependent on the power ratings of the specific PSU? Or are they minimal power rating specs for each type of connection? Thanks.

 

[Darkbreeze]

No, you would not. The GPU draws what it needs, and the bottom line is that you have a low end power supply anyhow, and shouldn't probably even be using it with any discreet graphics card, much less trying to gain more power. The PCI cables supply exactly what is needed by the GPU and if you have a PSU without the necessary number of 6 or 8 pin connectors, then it's unquestionably not fit for use with that particular card, regardless of model quality.

Your model has weak 12v rails, is made by FSP and is failure prone. What GPU card are you attempting to run with this unit?

 

[le modulor]

Thank you for ur reply Darkbreeze and sorry for my long winded answer below.

BTW, my PSU has two 6+2-Pin GPU cables. It has been running "flawlessly so far" a Sapphire HD 7850 2GB OCed at 1,050 MHz for the GPU Clock, 1,450 MHz for the Memory Clock and at +20% Power Limit (all max settings from the Catalyst Control Center). The rest of my system includes:

1) Intel Mobo DZ77RE-75K
2) i7-3770k CPU running at stock
3) two Samsung SSDs (250 GB 840 EVO and 512 GB 840 PRO) and a WD 2TD HD
4) 2x8GB Corsair RAM Vengeance Pro Series 1866MHz (unfortunately running in Single Channel because I have a damaged DIM Slot#1 on the Mobo and the RAM will only run in SIngle Channel in Slots #3 and #4)
5) Cooler Master Hyper 212 EVO CPU cooler
6) Corsair Carbide 500R case with all its 4 cooling fans running
7) and the infamous Gigabyte Superb E720 PSU with the four weak 12V 18Amp rails!

I dont want to bore you with the history of the choice for these components and I understand the limitations of both my PSU and of the now discontinued Intel Mobo DZ77RE-75K (which wouldn't even accept a mild OC of the i7-3770k).

My problem started when I tried to OC the HD 7850 a bit further using MSI Afterburner. The card is stable at 1,115 MHz for the GPU Clock and 1,450 MHz for the Memory Clock with the GPU temps below 65 Deg C and the GPU Fans never exceeding 45% of max speed. Anything more than that crashes the AMD Video Driver (Catalyst V15.7.1 installed). So, knowing that my PSU has a weak 12V rail but can, hopefully as advertised, power four weak 18Amp 12 V rails, I wanted to know if the crashes of the AMD Video Driver are:

1) due to the weak 12V rail, or
2) are due to my luck with the specific OC potential of my HD 7850 (1,115 MHz for the GPU Clock and 1,450 MHz for the Memory Clock)

As u know, the typical max power rating of the 6-Pin connection is 75W (way below the theoretical max power delivery of 216W for only one of the four 12V 18Amp rails of my poor PSU). The Mobo can supply another 75W thru the PCI-E 3.0x16 slot so the HD 7850 could theoretically receive a total of 150W, a healthy 15% above its TDP rating of 130W. I also understand that OCing the GPU will probably increase its power requirements above its spec TDP.

So my query is: assuming my OC limiting variable is power delivery to the GPU above the max 150W that can be supplied by both the 6-Pin connection and the PCI-E 3.0x16 slot, could I coax a bit more power into the HD 7850 by swapping the 6-Pin connection with the "two Molex to 6-Pin adapter" that came with the HD 7850 (and that I never needed to use before). Assuming each Molex is running at 6Amp (the lower end of their Amp rating of 6 Amp to 10 Amp), two Molexs could theoretically deliver up to 144W, almost double the 75W max rating of the 6-Pin connection.

or an alternative is to stop wasting time and upgrade the Mobo, PSU, OC the CPU and get a more modern midrange GPU (GTX 970 or AMD R9 390).

Thanks.

 

[Darkbreeze]

The first thing I'd try is increasing the fan speed profile to stay on max at all times, just to see if thermal issues are the problem.

I'd also do a clean GPU card driver as follows. Driver conflicts due to residual registry entries being present can easily bork a system.

http://www.tomshardware.com/faq/id-2767677/clean-graphics-driver-install-windows.html


Also manually check your mobo bios version to see that it's got the latest one.

 

[le modulor]

OK, will do. Thank you for the link.
I am guessing you do not think the issue is not enough power being delivered to the HD 7850?
Again, thank you for your patience.

 

[Darkbreeze]

Unless the power supply has a problem, it's rated capacity is not the problem. The E720 is known to only sustain about 540w or 45amps, but that should be enough for the HD 7850 which calls for 37amps or a 450w unit of high quality and sufficient connectors.

PSU could still be the problem, but I'd try those things above first. Might be a good idea to see if the system voltages are listed in the bios, or download HWinfo and run "sensors only". Don't use HWmonitor or Open hardware monitor if you don't have to as they tend to misread sensors on some chipsets.

You're looking for the +3, +5 and +12v readings.

 

[le modulor]

Ok, thank you. Will follow ur suggestions and report back if I reach any conclusions.

 

[Darkbreeze]

Sounds good.

 

[le modulor]

I used Intel Desktop Utilities. These are the voltage readouts (while gaming):

1) +12V: 12.030V (drops occasionally to 11.900V)
2) +5V: 5.160V (increases occasionally to 5.190V)
3) +3.3V: 3.370V (steady)
4) Memory Voltage: 0.750V (steady)
5) +3.3V Standby: 3.310V (steady)

Any apparent issues?

Thanks.

 

[Darkbreeze]

Nope. Looks fine. Try recording the same readings with the system under a severe gaming load.