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CPU Voltages Affecting GPU

Jeremytroid
By Jeremytroid
in Graphics Cards
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I've been experimenting with undervolting recently and have come up with some strange issues. (Same rig as in the signature by the way)

 

After searching around a bit, the lowest stable voltages on a 965 seem to be around 1.1175V. However, when lowering mine past 1.2V, the system fails to post. All of the fans spin up, however the GPU fan will spin up to a higher RPM, then return to normal and spin up again. This loop doesn't stop until turning off the machine. To get my computer to start up again, I have to remove the CMOS battery and motherboard power. Interestingly, for the few short days that I had the 650 Ti Boost, I could lower the CPU voltage lower without issue.

 

*Note: I only modified the CPU voltage. Everything else is at stock.

 

Thoughts or suggestions?

CPU: Intel Core i7 4790S 3.2/4.0 GHz  GPU: HIS AMD Radeon R9 285 2GB GDDR5  Motherboard: ASUS Pro Gamer H97  RAM: 16 GB Corsair Vengeance DDR3 1600MHz  

PSU: NZXT HALE82 700W  Cooler: ZALMAN CNPS5X Performa  Case: NZXT H230 

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So let me get this straight. Before 650 Ti = can't post under 1.1175. After 650 TI = posts successfully? that is.....weird.

3x Dell U2412M |Silverstone FT03 | Maximus V Gene | 3770K @ 4.5Ghz 1.2V | SLI GTX780 | Mushkin Ridgeback 8GB 1600 CL7 | Corsair AX760

 

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So let me get this straight. Before 650 Ti = can't post under 1.1175. After 650 TI = posts successfully? that is.....weird.

Nah, 1.1175V is the absolute lowest, stable voltage that a 965 will run at. With the 7750, my comp fails to post under only 1.2V. Yeah it's really strange. I was considering it may have to do with the fact that the 7750 draws all of it's power from the PCI slot, whereas the 650Ti Boost has a 6 pin connector.

CPU: Intel Core i7 4790S 3.2/4.0 GHz  GPU: HIS AMD Radeon R9 285 2GB GDDR5  Motherboard: ASUS Pro Gamer H97  RAM: 16 GB Corsair Vengeance DDR3 1600MHz  

PSU: NZXT HALE82 700W  Cooler: ZALMAN CNPS5X Performa  Case: NZXT H230 

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Nah, 1.1175V is the absolute lowest, stable voltage that a 965 will run at. With the 7750, my comp fails to post under only 1.2V. Yeah it's really strange. I was considering it may have to do with the fact that the 7750 draws all of it's power from the PCI slot, whereas the 650Ti Boost has a 6 pin connector.

I didn't even realise the 7750 didn't have any PCI connectors. that would make a lot of sense....maybe your actual voltage with the 7750 was lower even though it was set to the same setting in the BIOS. Set the voltage to 1.2 and look at what cpu-z reads. If the idle voltages are different between the 7750 and a different card (doesn't have to be a 650Ti)  then you have your answer. :)

3x Dell U2412M |Silverstone FT03 | Maximus V Gene | 3770K @ 4.5Ghz 1.2V | SLI GTX780 | Mushkin Ridgeback 8GB 1600 CL7 | Corsair AX760

 

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CPU shouldn't even be affected by the GPU at all. Doesn't matter if it's pulling all the power from the PCI-E slot. A 650 Ti pulls power from the slot and the 6 pin. The CPU has its own power connection.

"It pays to keep an open mind, but not so open your brain falls out." - Carl Sagan.

"I can explain it to you, but I can't understand it for you" - Edward I. Koch

"I didn't die! I performed a tactical reset!" - Apollolol

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CPU shouldn't even be affected by the GPU at all. Doesn't matter if it's pulling all the power from the PCI-E slot. A 650 Ti pulls power from the slot and the 6 pin. The CPU has its own power connection.

Yeah I suspected that too. I have know idea why it happens. I unfortunately can't test any other cards since I melted my Boost and my 6570 is being lent to a friend.

 

Thanks for the ideas Giac, I'll try it out when I can!

CPU: Intel Core i7 4790S 3.2/4.0 GHz  GPU: HIS AMD Radeon R9 285 2GB GDDR5  Motherboard: ASUS Pro Gamer H97  RAM: 16 GB Corsair Vengeance DDR3 1600MHz  

PSU: NZXT HALE82 700W  Cooler: ZALMAN CNPS5X Performa  Case: NZXT H230 

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Yeah I suspected that too. I have know idea why it happens. I unfortunately can't test any other cards since I melted my Boost and my 6570 is being lent to a friend.

 

Thanks for the ideas Giac, I'll try it out when I can!

And I don't have any cards with me to lend you. Oh well.

"It pays to keep an open mind, but not so open your brain falls out." - Carl Sagan.

"I can explain it to you, but I can't understand it for you" - Edward I. Koch

"I didn't die! I performed a tactical reset!" - Apollolol

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Yeah I suspected that too. I have know idea why it happens. I unfortunately can't test any other cards since I melted my Boost and my 6570 is being lent to a friend.

 

Thanks for the ideas Giac, I'll try it out when I can!

You kinda answered the question for yourself...

3x Dell U2412M |Silverstone FT03 | Maximus V Gene | 3770K @ 4.5Ghz 1.2V | SLI GTX780 | Mushkin Ridgeback 8GB 1600 CL7 | Corsair AX760

 

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You kinda answered the question for yourself...

I know, I was hoping someone had some kind of magical wisdom to pass on :3

CPU: Intel Core i7 4790S 3.2/4.0 GHz  GPU: HIS AMD Radeon R9 285 2GB GDDR5  Motherboard: ASUS Pro Gamer H97  RAM: 16 GB Corsair Vengeance DDR3 1600MHz  

PSU: NZXT HALE82 700W  Cooler: ZALMAN CNPS5X Performa  Case: NZXT H230 

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