Power draw query for BIOS flashing

[Jaqen]

I recently setup a custom liquid cooling loop for my SLI'd gtx 970's and decided to do a bit more overclocking.

 

Currently both cards are 

 

CORE:1527mhz

MEM:8000mhz effective

VOLT:+87mv

BIOS MODDED POWER LIMIT: 150%

 

I would initially hit a hard power limit of 100% on the cards and so modded the bios to 120% but after this the cards were still throttling at 110% and would not hold a constant Core Clock so I went back and flashed the bios again to 150% accordingly

 

STANDARD BIOS: PCIE-75000

                              6-pin-75000

                              6-pin-75000

                   TOTAL TDP-250000

 

MODDED BIOS: PCIE-86000

                           6-pin-94500

                           6-pin-94500

               TOTAL TDP-271000

 

Once I did this I no longer hit a power limit on the cards and instead see VREL, VOP + SLI in GPU-Z at 115% max TDP. I also have a constant 1527mhz on the core now.

 

My question is this... Where are my cards getting the extra power from if 6-pin power connectors are rated for 75W and the PCI-E is rated at 75W?

Why is the stock BIOS on these cards set to draw 235W max if the 970 is only supposed to draw max 180W?

 

Motherboard:Asus maximus ranger vii

CPU: i5 4690k at 4.5ghz

16gb kinston 1600mhz

2x palit jetstream gtx 970's SLI (LIQUID COOLED)

480gb SSD

2TB HDD

CORSAIR RM850

[Lays]

You're over-currenting your PCI-E lanes. I would not recommend this without plugging in one of those 6 pin things that some motherboards have near their PCIE lanes.

 

Also, you can push more current than the "spec" given by PSU manufacturers, you can easily pull more power through 6 pins and 8 pins than they're actually rated for. As long as you have a quality PSU it's all good.

One thing you should monitor if you push more current through your 6 and 8 pin:  get something such as HWINFO 64, and monitor your PSU's voltages while your GPU's are under load.  You should be able to monitor your 3v/5v/12v voltages, and see how your PSU reacts to the higher power draw through the connectors.

[Jaqen]

You're over-currenting your PCI-E lanes. I would not recommend this without plugging in one of those 6 pin things that some motherboards have near their PCIE lanes.

 

Also, you can push more current than the "spec" given by PSU manufacturers, you can easily pull more power through 6 pins and 8 pins than they're actually rated for. As long as you have a quality PSU it's all good.

One thing you should monitor if you push more current through your 6 and 8 pin:  get something such as HWINFO 64, and monitor your PSU's voltages while your GPU's are under load.  You should be able to monitor your 3v/5v/12v voltages, and see how your PSU reacts to the higher power draw through the connectors.

so would you suggest reducing the PCI-e lane power back down to 75000 and then add a bit more to the power connectors? and is it not true that PCI-E 3.0 can deliver more than 75W?

[Jaqen]

I also read here that most 6-pin power connectors have the 3rd 12v pin active as apposed to the standard specification where it is left unused.. anyone know about this?

[Lays]

so would you suggest reducing the PCI-e lane power back down to 75000 and then add a bit more to the power connectors? and is it not true that PCI-E 3.0 can deliver more than 75W?

 

 

I'd leave your PCI-E lanes at the 75W, it's much safer from what I've seen to add that extra wattage to your 8 pin and 6 pin.

 

I myself, among others on high end cards have ran 400-500W BIOS with 2 8 pins and never had any issues.

 

My 780 Lightning was pulling 434w with a 900W Ln2 BIOS on it when I was benching at 1.375 volts in unigine valley, and it just had 2 8 pins on it.

[Jaqen]

ok sounds good, my cards have 2 6-pin connectors and I have been reading up about them, the only difference between 6-pin and 8-pin seems to be the ground wires so theoretically a 6-pin can provide 150W the same as 8-pin although apparently the resistance is different so it would seem like a good idea to feel the connectors themselves and make sure they don't get hot.

 

If I draw 100w from each 6-pin and then leave the PCI-E AT 75W I think I should be fine. I am still confused as to why in the stock BIOS the total TDP was set to 250W when the total from each was only adding up to 235W

[0x1e]

Leave the PCI-e at 75 watts.

PCI-e 3.0 can not deliver more voltage / wattage than 2.0 , it's just a faster connection but that's about it. You can burn out the 24 pin power connection, traces on the motherboard or the pci-e ports. That's why they began adding those molex / 6 pin power connections for pci-e ports.

Take the extra power from the 6 pin / 8 pin power. If you have a good quality psu then you'll be fine.