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Overclock (i7 950 to 4GHz) Causing high DPC Latency - Why?

post #1 of 30
Thread Starter 
Hi

I am trying to OC an i7 950 to 4GHz and running into a weird DPC latency problem causing audio crackling. The overclock seems to be stable enough (no BSOD/freeze/crash while gaming), but when I play a game DPC latency becomes a real issue. If I set BIOS to "optimised defaults", then there are no DPC issues at all.

I have tried numerous things:
  • Unplug power cables from PSU and mobo, use duster on the plugs
  • Try different sockets on the PSU
  • Swap RAM sticks around
  • Plug GPU to another socket
  • Disable virtualisation, HPET
  • Reinstall GPU, chipset, audio, network, USB drivers
  • Run sfc /scannow and chkdsk /R /F


Hardware:
  • GA-X58A-UD3R (rev. 2.0)
  • Intel i7 950
  • 1600 MHz Corsair RAM 9-9-9-24 1.5v, two sets of 3x4GB (made sure that each set occupies a single RAM slot colour)
  • Gigabyte GTX 980 Ti
  • Corsair HX 850i


Set up:
  • Primary monitor with for gaming / movies is via DVI
  • Secondary monitor for Chrome and other things is via HDMI
  • Sound is via USB2 SteelSeries Siberia soundcard
  • nVidia HD audio and Realtek HD audio are both disabled in Device Manager
  • Azalia audio is disabled in BIOS
  • nVidia global config is attached
  • nVidia PowerMizer is disabled


Conditions:
  • Chrome is open (when it isn't, there are fewer DPC spikes, but there still are plenty)
  • To test, I'm running Overwatch in 1920x1080 fullscreen windowed at all ultra settings
  • Also Witcher 3 all ultra settings except nVidia HairWorks AA on only 2 but with better shadow settings than default ultra ones
  • Also Prime95 blend tests

Optimised Default settings:
Code:
CPU Clock Ratio........................[21.0]
QPI Clock Ratio........................[Auto]
Uncore Clock Ratio.....................[Auto]
BLCK...................................[Auto]
System Memory Multiplier (SPD).........[Auto]
PCI Express Frequency (MHz)............[Auto]

CPU Clock Drive........................[800mV]
PCI Express Clock Drive................[900mV]
CPU Clock Skew.........................[0ps]
IOH Clock Skew.........................[0ps]

Load Line Calibration (LLC)............[Standard]
CPU Vcore..............................[Auto]
QPI/Vtt Voltage........................[Auto]
CPU PLL................................[Auto]
PCIE...................................[Auto]
QPI PLL................................[Auto]
IOH Core...............................[Auto]
ICH I/O................................[Auto]
ICH Core...............................[Auto]

DRAM Voltage...........................[Auto]
DRAM Termination.......................[Auto]
Ch-A Data VRef.........................[Auto]
Ch-B Data VRef.........................[Auto]
Ch-C Data VRef.........................[Auto]
Ch-A Address VRef......................[Auto]
Ch-B Address VRef......................[Auto]
Ch-C Address VRef......................[Auto]

XMP....................................[Profile1]
Performance Enhance....................[Turbo]
DRAM Timing Selectable.................[Auto]

Intel Turbo Boost Tech.................[Enabled]
CPU Cores Enabled......................[All]
CPU Multi-threading....................[Enabled]
CPU Enhanced Halt (C1E)................[Enabled]
C3/C6/C7 State Support.................[Disabled]
CPU Thermal Monitor....................[Enabled]
CPU EIST Function......................[Enabled]
Bi-Directional PROCHOT.................[Enabled]
Isochronous Support....................[Enabled]
Virtualization Technology..............[Enabled]


Overclocked Settings (mostly where different from above):
Code:
CPU Clock Ratio........................[21.0]
Uncore Clock Ratio.....................[x16]
BLCK...................................[191]
System Memory Multiplier (SPD).........[8.0]
PCI Express Frequency (MHz)............[100]

Load Line Calibration (LLC)............[Level 2]
CPU Vcore..............................[1.33750]
QPI/Vtt Voltage........................[1.335]
CPU PLL................................[1.840]
PCIE...................................[1.500]
QPI PLL................................[1.100]
IOH Core...............................[1.100]

DRAM Voltage...........................[1.500]

XMP....................................[Disabled]
Performance Enhance....................[Standard]
DRAM Timing Selectable.................[Quick]
Channel Interleaving...................[Auto]
Rank Interleaving......................[Auto]

CAS Latency Time (tCL).................[9]
tRCD...................................[9]
tRP....................................[9]
tRAS...................................[24]

CPU EIST Function......................[Disabled]


Running with Optimised Default settings:
  • Idling RealTemp shows 38C average
  • Prime95 runs fine for at least 40 minutes and RealTemp shows 70C average
  • Gaming DPC Latency Checker shows average under 200; RealTemp shows average 63C, max 70C


Running with OC settings:
  • Idling RealTemp shows 48C average
  • Prime95 runs fine for at least 10 minutes (didn't dare run it longer with temps reaching 98C - my CPU cooler is not great)
  • Gaming DPC Latency Checker shows bad latency, average spikes around 25,000; RealTemp shows average 70C, max 78C
  • DPC stats via WPA are attached, the most latency seems to come from dxgkrnl.sys


Any ideas what could be causing the DPC latency?

Thanks

P.S. From what I read, tRAS = tCL+tRCD+tRP, which is not the case in pretty much any BIOS settings I've seen - tRAS is always smaller than that. And even when the RAM stick has 9-9-9-24, 24 < 27 obviously, so I find this a little confusing.

DPC Screenshots:


Edited by Shoujin - 6/29/16 at 7:26am
post #2 of 30

It's probably not stable. With an overclock this high, you would need to test it properly with an extremely long run of Prime95, meaning, long enough for it to get through ALL of its different FFTs at least once (there were 82 of them the last time I checked). 10 minutes is pretty much a waste of time and doesn't determine any kind of stability whatsoever. For that matter, neither does 40 minutes.

 

You see, good stability testing programs like Prime95 don't put a constant unchanging load on the CPU. So, the effectiveness of the test can't be judged by time - just as I eluded to.

 

The best way to use Prime95 is by selecting Blend and then selecting Custom so that you create what we like to call the "Custom Blend" test. Then where it allows you choose how much memory to use, you should enter approximately 80-85% of your installed memory. The more memory you can free up for Prime95, the better.

 

So yeah, you're going to need better CPU cooling if you want to overclock this high. You didn't say what you have for cooling, but reaching 98 degrees after only 10 minutes is bad. I would stop overclocking until you can acquire a proper CPU cooler for overclocking.


Edited by TwoCables - 6/29/16 at 6:33am
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CPUMotherboardGraphicsRAM
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post #3 of 30
Thread Starter 
Sure, I need to get a better cooler.

However, are there any particular causes for DPC latency? Can it be caused by unstable OC by itself?

Could you suggest any changes to the configuration, please? I'm pretty noobish at this.
post #4 of 30
Quote:
Originally Posted by Shoujin View Post

Sure, I need to get a better cooler.

However, are there any particular causes for DPC latency? Can it be caused by unstable OC by itself?

Could you suggest any changes to the configuration, please? I'm pretty noobish at this.

 

I've never checked DPC latency when overclocking. All I'm trying to say is, you only tested it with some gaming and 10 minutes of Prime95. That's not good, unfortunately. The only possible recommendation I can come up with is increasing the core voltage, but you need much better cooling so I can't recommend that. Your idle temp alone looks like you're using Intel's stock cooler.

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i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
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PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
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Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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post #5 of 30
Thread Starter 
The problem is the crackling audio due to high DPC latency, which is seemingly happening only if OC settings are applied.
What I am trying to do is establish whether it is actually the OC that causes it and figure out which exact OC settings may be related to it.

Stability testing right now is not necessarily the answer as it won't be able to address those two questions.

70C should not be too high alone to cause DPC latency, right?
post #6 of 30

I am trying to say that it's not stable. I'm trying to say that instability is very likely the cause here because you haven't even really truly tested the stability. In order to have any hope of stabilizing it, you'd very likely need to increase the voltage, but you can't do that because your cooling is no better than Intel's stock cooling. So, you shouldn't even be overclocking at all right now. Your temps while running Prime95 hit 98 after only 10 minutes. That looks like Intel's stock cooler to me.

 

So I'm trying to tell you, just get a better cooler, then you can start doing things like increasing the voltage and running proper stability tests.

 

Edit: You have to think about it like this: we have no way to rule out instability right now because your temps get dangerously high after only 10 minutes of a basic Blend test. That's enough to kill stability while running Prime95, which would mean you'd never know if a failed Prime95 run was caused by heat or not enough voltage. Y'know? The bottom line is, you need proper CPU cooling for overclocking in order to continue. That way, you could do a proper Prime95 test to see if it's stable. If it's stable, then we start looking for other culprits. I would bet that your computer would fail a proper run in Prime95 though unless you got lucky and happened to have created stable settings right away. It happens, but you have to be lucky for that.

 

In other words, if we find that it's not stable, then we can instantly know that the high DPC is caused by instability - which is what I'm betting on. Why else would things not be working correctly while the CPU is overclocked to 4 GHz?


Edited by TwoCables - 6/29/16 at 7:29am
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Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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It's a computer!
(18 items)
 
  
CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
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Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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post #7 of 30
Thread Starter 
It is a good way to look at it, thanks for clarifying (really appreciate the edit).
Quote:
You didn't say what you have for cooling
It seems to be Corsair A50 (at least looks like it), but I don't remember with absolute certainty. It definitely isn't a stock cooler.
Quote:
unless you got lucky and happened to have created stable settings right away
It actually isn't the first iteration, I did experience some BSODs and freezes in Prime while getting to this config.

Should I try a liquid cooler like Corsair H100i or 110? I will probably need to research coolers a bit more, as I see that people complain these two are pretty loud.
post #8 of 30
Quote:
Originally Posted by Shoujin View Post

It is a good way to look at it, thanks for clarifying (really appreciate the edit).
It seems to be Corsair A50 (at least looks like it), but I don't remember with absolute certainty. It definitely isn't a stock cooler.
It actually isn't the first iteration, I did experience some BSODs and freezes in Prime while getting to this config.

Should I try a liquid cooler like Corsair H100i or 110? I will probably need to research coolers a bit more, as I see that people complain these two are pretty loud.

 

You're very welcome.

 

Yeah, the A50 is really just for replacing a stock cooler but it's not for overclocking. You could probably do some light overclocking, but nothing like what you're trying to do! I don't know what the best cooler is these days, so yeah I think some research may be needed unless we get lucky and get answers from people in this thread.

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Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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It's a computer!
(18 items)
 
  
CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
CoolingOSMonitorKeyboard
Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
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post #9 of 30
Thread Starter 
While you are around, can I ask you something else?

Occasionally my machine would go into a boot loop and will not even reach POST. The only way to get it out of it is to cut the power to PSU, wait for a few seconds, then turn it back on. Then, in the POST screen it would tell me that there was a failure due to overclocking or voltage and reset CMOS to safe defaults.

If this is due to an unstable OC, why does this not happen all the time, or why would there be no BSOD, but an occasional boot loop? Is there any particular setting to look into? So far I mostly saw people interested of just getting out of the loop (not a problem here); and somebody suggested that capacitors could be overly charged. The last suggestion would imply I need to lower the voltage somewhere, right?
post #10 of 30
Quote:
Originally Posted by Shoujin View Post

While you are around, can I ask you something else?

Occasionally my machine would go into a boot loop and will not even reach POST. The only way to get it out of it is to cut the power to PSU, wait for a few seconds, then turn it back on. Then, in the POST screen it would tell me that there was a failure due to overclocking or voltage and reset CMOS to safe defaults.

If this is due to an unstable OC, why does this not happen all the time, or why would there be no BSOD, but an occasional boot loop? Is there any particular setting to look into? So far I mostly saw people interested of just getting out of the loop (not a problem here); and somebody suggested that capacitors could be overly charged. The last suggestion would imply I need to lower the voltage somewhere, right?

 

This is getting past my knowledge, but maybe you can see what happens when you have all voltages set to Auto except for the VCore and maybe also the DRAM. I've never overclocked this generation of CPUs, so I'm stretching myself a bit.

It's a computer!
(18 items)
 
  
CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
CoolingOSMonitorKeyboard
Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
AudioAudio
X-Fi Titanium HD Klipsch ProMedia 2.1 (with 16 AWG Monster Cable... 
  hide details  
Reply
It's a computer!
(18 items)
 
  
CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.368-1.384V fixed voltage) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (OS) 3 TB Toshiba P300 (storage) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
CoolingOSMonitorKeyboard
Thermaltake Frio Win 7 Home Premium x64 SP1 Retail AOC G2460PG (24" 1920 x 1080 144Hz G-SYNC) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Intellimouse Optical (1.1A) 1000Hz polling rate Basic, but premium round 
AudioAudio
X-Fi Titanium HD Klipsch ProMedia 2.1 (with 16 AWG Monster Cable... 
  hide details  
Reply
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