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PCH Voltage helps with GPU OC - Z68 Chipset Sandy Bridge

post #1 of 7
Thread Starter 
Hi all,

I've been looking around for a while now but cannot find anything that would explain my experience with overclocking my SLI MSI GTX 580 Lightning Xtreme. So I thought I'd make a post here and hopefully someone will shed some light into my curious experience.

In the beginning, I find that whenever I push the GPU core voltages to anything over +136 in MSI Afterburner, it would crash when gaming, even with stock clock. I deduced that somehow the GPUs must be lacking power from a certain source outside of MSI Afterburner.

I then looked around the bios and found the PCH voltage, which from what I've read, governs communications for all PCIE & USB hubs EXCEPT GPUs. I thought I'd give it a try anyway, and raised it up to 1.15. Viola! my GPUs are now Heaven and gaming stable at +166 voltage.

Later on I've added waterblocks to the GPUs and wanted to max out voltages allowable in MSI Afterburner. I pushed it to +200, and it crashed even with clock which was previously stabled at +166 volts! So I instinctively went back into BIOS, and upped the PCH to 1.2, came back and Bingo! I am now Heaven and gaming stable at 990mhz.

My question is, why would PCH voltages help at all? From every source I've read, it doesn't affect GPUs.
Nebula
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Nebula
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post #2 of 7

what mobo are you running that your experiencing this with?

 

 Seems odd though.. what bclk are you running with your setup? 


Edited by CL3P20 - 11/21/12 at 5:37pm
post #3 of 7
Thread Starter 
Mobo: Asus p8z68-v Pro Gen3 revision: D2
CPU: 2700k

Yeah it's very odd. BCLK is at 100. Didn't change it at all. It was OC'ed to 5ghz @ 1.43 ~ 1.44 Vcore using multipliers only.
Edited by Sashimi - 11/21/12 at 5:42pm
Nebula
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Nebula
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post #4 of 7

Only thing I can say off-hand is that your GPU's are using more of the available PCI-E bandwidth than the PCH could cope with at the previous voltage...especially considering you didnt change bclk.. that would be my only plausible explanation for it.

post #5 of 7
Thread Starter 
That's what it would appears, however I from what I've read video cards don't pass through PCH.

http://www.masterslair.com/vcore-vtt-dram-pll-pch-voltages-explained-core-i7-i5-i3/

http://www.overclock.net/t/1089576/pch-voltage

So I'm curious. Could these sources be false?
Nebula
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Optical DriveCoolingCoolingCooling
Pioneer BDR-206BK 12X Blu-Ray Writer Drive Koolance RP-452X2 Dual 5.25in Reservoir for 1-2... Koolance 450s Pump Koolance 450s Pump 
CoolingCoolingCoolingCooling
EK Supreme HF Bitspower Black Freezer Acrylic Top With Clear ... Bitspower Black Freezer Acrylic Top With Clear ... Black Ice GTX 240 Radiator 
CoolingCoolingCoolingCooling
Black Ice GTX 480 Radiator Koolance CTR-SPD24X2 Dual 24V Pump Controller Nidec Servo Scythe Gentle Typhoon 120mm Case Fa... Xigmatek Crystal Red LED 140mm Case Fan 1000RPM 
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Samsung SyncMaster 740N 17" Azio Levetron Mech 5 Mechanical Gaming Keyboard Cooler Master Silent Pro Hybrid 1300W Aerocool X-Predator Evil Black Edition 
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Nebula
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MSI N580GTX Lightning Xtreme 3GB Edition G.Skill RipjawX F3-17000CL9D-8GBXM Western Digital Caviar Black 2TB 7200RPM Seagate Barracuda LP 2TB 5900RPM 
Optical DriveCoolingCoolingCooling
Pioneer BDR-206BK 12X Blu-Ray Writer Drive Koolance RP-452X2 Dual 5.25in Reservoir for 1-2... Koolance 450s Pump Koolance 450s Pump 
CoolingCoolingCoolingCooling
EK Supreme HF Bitspower Black Freezer Acrylic Top With Clear ... Bitspower Black Freezer Acrylic Top With Clear ... Black Ice GTX 240 Radiator 
CoolingCoolingCoolingCooling
Black Ice GTX 480 Radiator Koolance CTR-SPD24X2 Dual 24V Pump Controller Nidec Servo Scythe Gentle Typhoon 120mm Case Fa... Xigmatek Crystal Red LED 140mm Case Fan 1000RPM 
CoolingCoolingOSMonitor
Bitfenix Spectre PRO Red LED 230mm Case Fan 900RPM Silverstone Air-Penetrator UV-Blue 120mm Case F... Windows 7 Home Premium 64 Bits Benq XL2410T 120hz 
MonitorKeyboardPowerCase
Samsung SyncMaster 740N 17" Azio Levetron Mech 5 Mechanical Gaming Keyboard Cooler Master Silent Pro Hybrid 1300W Aerocool X-Predator Evil Black Edition 
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post #6 of 7

well how can PCH "govern all PCIE communications.. " but not GPU's ..? I mean.. the bandwidth comes from the chipset interface right? Just like a CPU.. saturate it with a more intensive workload and it can become unstable.. sometimes requiring more voltage.

 

 PCH voltage must be linked with the PCIE controller internally.. like separate data planes on the same voltage divider/supply.

post #7 of 7
Thread Starter 
That's true. Evidences also suggest this. Also now that I think about it, I also have a sound card and network card plugged into the PCI/PCI-E expansion slots so that could stress the controller further.

I think this should be interesting to everyone who's in the same situation I was. I can genuinely verify that PCH helps with extreme GPU overclock, at least on the sandy bridge platform, despite many sources on the web that says it's not related.
Nebula
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MSI N580GTX Lightning Xtreme 3GB Edition G.Skill RipjawX F3-17000CL9D-8GBXM Western Digital Caviar Black 2TB 7200RPM Seagate Barracuda LP 2TB 5900RPM 
Optical DriveCoolingCoolingCooling
Pioneer BDR-206BK 12X Blu-Ray Writer Drive Koolance RP-452X2 Dual 5.25in Reservoir for 1-2... Koolance 450s Pump Koolance 450s Pump 
CoolingCoolingCoolingCooling
EK Supreme HF Bitspower Black Freezer Acrylic Top With Clear ... Bitspower Black Freezer Acrylic Top With Clear ... Black Ice GTX 240 Radiator 
CoolingCoolingCoolingCooling
Black Ice GTX 480 Radiator Koolance CTR-SPD24X2 Dual 24V Pump Controller Nidec Servo Scythe Gentle Typhoon 120mm Case Fa... Xigmatek Crystal Red LED 140mm Case Fan 1000RPM 
CoolingCoolingOSMonitor
Bitfenix Spectre PRO Red LED 230mm Case Fan 900RPM Silverstone Air-Penetrator UV-Blue 120mm Case F... Windows 7 Home Premium 64 Bits Benq XL2410T 120hz 
MonitorKeyboardPowerCase
Samsung SyncMaster 740N 17" Azio Levetron Mech 5 Mechanical Gaming Keyboard Cooler Master Silent Pro Hybrid 1300W Aerocool X-Predator Evil Black Edition 
MouseAudioOtherOther
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Nebula
(33 items)
 
  
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Intel Core i7 2700K Intrel Core i7 2700K Asus p8z68-v Pro Gen3 MSI N580GTX Lightning Xtreme 3GB Edition 
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MSI N580GTX Lightning Xtreme 3GB Edition G.Skill RipjawX F3-17000CL9D-8GBXM Western Digital Caviar Black 2TB 7200RPM Seagate Barracuda LP 2TB 5900RPM 
Optical DriveCoolingCoolingCooling
Pioneer BDR-206BK 12X Blu-Ray Writer Drive Koolance RP-452X2 Dual 5.25in Reservoir for 1-2... Koolance 450s Pump Koolance 450s Pump 
CoolingCoolingCoolingCooling
EK Supreme HF Bitspower Black Freezer Acrylic Top With Clear ... Bitspower Black Freezer Acrylic Top With Clear ... Black Ice GTX 240 Radiator 
CoolingCoolingCoolingCooling
Black Ice GTX 480 Radiator Koolance CTR-SPD24X2 Dual 24V Pump Controller Nidec Servo Scythe Gentle Typhoon 120mm Case Fa... Xigmatek Crystal Red LED 140mm Case Fan 1000RPM 
CoolingCoolingOSMonitor
Bitfenix Spectre PRO Red LED 230mm Case Fan 900RPM Silverstone Air-Penetrator UV-Blue 120mm Case F... Windows 7 Home Premium 64 Bits Benq XL2410T 120hz 
MonitorKeyboardPowerCase
Samsung SyncMaster 740N 17" Azio Levetron Mech 5 Mechanical Gaming Keyboard Cooler Master Silent Pro Hybrid 1300W Aerocool X-Predator Evil Black Edition 
MouseAudioOtherOther
Logitech G9X Gaming Mouse Auzentech X-Meridian 7.1 2G Lamptron FC5 V2 Fan Controller Bitspower Dual 20cm Cold Cathode Kit UV 
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